diff --git a/modules/openapi-generator/src/main/resources/JavaSpring/beanValidationHeaderParams.mustache b/modules/openapi-generator/src/main/resources/JavaSpring/beanValidationHeaderParams.mustache
new file mode 100644
index 000000000000..a2f19f77468c
--- /dev/null
+++ b/modules/openapi-generator/src/main/resources/JavaSpring/beanValidationHeaderParams.mustache
@@ -0,0 +1 @@
+{{#required}}@NotNull {{/required}}{{^useOptional}}{{>beanValidationCore}}{{/useOptional}}{{#useOptional}}{{#required}}{{>beanValidationCore}}{{/required}}{{/useOptional}}
\ No newline at end of file
diff --git a/modules/openapi-generator/src/main/resources/JavaSpring/headerParams.mustache b/modules/openapi-generator/src/main/resources/JavaSpring/headerParams.mustache
index b5ff71e03857..b0bb8ac20ffc 100644
--- a/modules/openapi-generator/src/main/resources/JavaSpring/headerParams.mustache
+++ b/modules/openapi-generator/src/main/resources/JavaSpring/headerParams.mustache
@@ -1 +1 @@
-{{#isHeaderParam}}{{>paramDoc}} @RequestHeader(value = "{{baseName}}", required = {{#required}}true{{/required}}{{^required}}false{{/required}}{{#defaultValue}}, defaultValue = "{{{.}}}"{{/defaultValue}}){{>dateTimeParam}} {{>optionalDataType}} {{paramName}}{{/isHeaderParam}}
\ No newline at end of file
+{{#isHeaderParam}}{{#useBeanValidation}}{{>beanValidationHeaderParams}}{{/useBeanValidation}}{{>paramDoc}} @RequestHeader(value = "{{baseName}}", required = {{#required}}true{{/required}}{{^required}}false{{/required}}{{#defaultValue}}, defaultValue = "{{{.}}}"{{/defaultValue}}){{>dateTimeParam}} {{>optionalDataType}} {{paramName}}{{/isHeaderParam}}
\ No newline at end of file
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java
index ac058ecd2ba8..844193c791ac 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java
@@ -654,7 +654,7 @@ public void testMultipartCloud() throws IOException {
                "List<MultipartFile> files",
                "MultipartFile file");
     }
-    
+
     @Test
     public void testRequestMappingAnnotation() throws IOException {
         final SpringCodegen codegen = new SpringCodegen();
@@ -1499,4 +1499,62 @@ public void shouldGenerateDiscriminatorFromAllOfWhenUsingLegacyDiscriminatorBeha
                              "})";
         assertFileContains(Paths.get(output.getAbsolutePath() + "/src/main/java/org/openapitools/model/Pet.java"), jsonTypeInfo, jsonSubType);
     }
+
+    @Test
+    public void shouldGenerateBeanValidationForHeaderParams_issue12726() throws IOException {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        OpenAPI openAPI = new OpenAPIParser()
+                .readLocation("src/test/resources/3_0/spring/issue_12726.yml", null, new ParseOptions()).getOpenAPI();
+        SpringCodegen codegen = new SpringCodegen();
+        codegen.setLibrary(SPRING_BOOT);
+        codegen.setOutputDir(output.getAbsolutePath());
+        codegen.additionalProperties().put(SpringCodegen.USE_TAGS, "true");
+
+        ClientOptInput input = new ClientOptInput()
+                .openAPI(openAPI)
+                .config(codegen);
+
+        DefaultGenerator generator = new DefaultGenerator();
+        Map<String, File> files = generator.opts(input).generate().stream()
+                                           .collect(Collectors.toMap(File::getName, Function.identity()));
+        JavaFileAssert.assertThat(files.get("HeadersApi.java"))
+                      .assertMethod("headerBeanValidation")
+                      .hasParameter("patternHeader")
+                      .assertParameterAnnotations()
+                      .containsWithName("NotNull")
+                      .containsWithNameAndAttributes("Pattern", ImmutableMap.of(
+                              "regexp", "\"[0-9]+\"")
+                      )
+                      .containsWithNameAndAttributes("Parameter", ImmutableMap.of(
+                              "name", "\"patternHeader\"",
+                              "description", "\"\"",
+                              "required", "true")
+                      )
+                      .containsWithNameAndAttributes("RequestHeader", ImmutableMap.of(
+                              "value", "\"patternHeader\"",
+                              "required", "true")
+                      );
+
+        JavaFileAssert.assertThat(files.get("HeadersApi.java"))
+                      .assertMethod("headerBeanValidation")
+                      .hasParameter("minMaxHeader")
+                      .assertParameterAnnotations()
+                      .containsWithNameAndAttributes("DecimalMin", ImmutableMap.of(
+                              "value", "\"1\"")
+                      )
+                      .containsWithNameAndAttributes("DecimalMax", ImmutableMap.of(
+                              "value", "\"10\"")
+                      )
+                      .containsWithNameAndAttributes("Parameter", ImmutableMap.of(
+                              "name", "\"minMaxHeader\"",
+                              "description", "\"\"")
+                      )
+                      .containsWithNameAndAttributes("RequestHeader", ImmutableMap.of(
+                              "value", "\"minMaxHeader\"",
+                              "required", "false")
+                      );
+
+    }
 }
diff --git a/modules/openapi-generator/src/test/resources/3_0/spring/issue_12726.yml b/modules/openapi-generator/src/test/resources/3_0/spring/issue_12726.yml
new file mode 100644
index 000000000000..4b7c866dc6b8
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/spring/issue_12726.yml
@@ -0,0 +1,27 @@
+openapi: 3.0.0
+info:
+  version: 1.0.0
+  title: Header validation
+paths:
+  "/headers":
+    options:
+      operationId: headerBeanValidation
+      tags:
+        - headers
+      parameters:
+        - name: patternHeader
+          in: header
+          required: true
+          schema:
+            type: string
+            pattern: "[0-9]+"
+        - name: minMaxHeader
+          in: header
+          required: false
+          schema:
+            minimum: 1
+            maximum: 10
+            type: number
+      responses:
+        '204':
+          description: no content
diff --git a/samples/client/petstore/spring-cloud-date-time/src/main/java/org/openapitools/api/DefaultApi.java b/samples/client/petstore/spring-cloud-date-time/src/main/java/org/openapitools/api/DefaultApi.java
index 64c24b8def11..472901d1c292 100644
--- a/samples/client/petstore/spring-cloud-date-time/src/main/java/org/openapitools/api/DefaultApi.java
+++ b/samples/client/petstore/spring-cloud-date-time/src/main/java/org/openapitools/api/DefaultApi.java
@@ -54,7 +54,7 @@ public interface DefaultApi {
     ResponseEntity<Void> get(
         @ApiParam(value = "A date path parameter", required = true, defaultValue = "1972-01-01") @PathVariable("date") @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate date,
         @NotNull @ApiParam(value = "A date-time query parameter", required = true, defaultValue = "1973-12-19T03:39:57-08:00") @Valid @RequestParam(value = "dateTime", required = true, defaultValue = "1973-12-19T03:39:57-08:00") @DateTimeFormat(iso = DateTimeFormat.ISO.DATE_TIME) OffsetDateTime dateTime,
-        @ApiParam(value = "A date header parameter", required = true, defaultValue = "1974-01-01") @RequestHeader(value = "X-Order-Date", required = true, defaultValue = "1974-01-01") @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate xOrderDate,
+        @NotNull @ApiParam(value = "A date header parameter", required = true, defaultValue = "1974-01-01") @RequestHeader(value = "X-Order-Date", required = true, defaultValue = "1974-01-01") @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate xOrderDate,
         @ApiParam(value = "A date cookie parameter", defaultValue = "1975-01-01") @CookieValue(name = "loginDate", required = false, defaultValue = "1975-01-01") @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate loginDate
     );
 
diff --git a/samples/openapi3/client/petstore/spring-cloud-date-time/src/main/java/org/openapitools/api/DefaultApi.java b/samples/openapi3/client/petstore/spring-cloud-date-time/src/main/java/org/openapitools/api/DefaultApi.java
index 6f2d649c5e1c..7416f84a3ffa 100644
--- a/samples/openapi3/client/petstore/spring-cloud-date-time/src/main/java/org/openapitools/api/DefaultApi.java
+++ b/samples/openapi3/client/petstore/spring-cloud-date-time/src/main/java/org/openapitools/api/DefaultApi.java
@@ -59,7 +59,7 @@ public interface DefaultApi {
     ResponseEntity<Void> get(
         @Parameter(name = "date", description = "A date path parameter", required = true) @PathVariable("date") @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate date,
         @NotNull @Parameter(name = "dateTime", description = "A date-time query parameter", required = true) @Valid @RequestParam(value = "dateTime", required = true, defaultValue = "1973-12-19T03:39:57-08:00") @DateTimeFormat(iso = DateTimeFormat.ISO.DATE_TIME) OffsetDateTime dateTime,
-        @Parameter(name = "X-Order-Date", description = "A date header parameter", required = true) @RequestHeader(value = "X-Order-Date", required = true, defaultValue = "1974-01-01") @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate xOrderDate,
+        @NotNull @Parameter(name = "X-Order-Date", description = "A date header parameter", required = true) @RequestHeader(value = "X-Order-Date", required = true, defaultValue = "1974-01-01") @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate xOrderDate,
         @Parameter(name = "loginDate", description = "A date cookie parameter") @CookieValue(name = "loginDate", required = false, defaultValue = "1975-01-01") @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate loginDate
     );
 
diff --git a/samples/openapi3/client/petstore/spring-cloud-oas3-fakeapi/src/main/java/org/openapitools/api/FakeApi.java b/samples/openapi3/client/petstore/spring-cloud-oas3-fakeapi/src/main/java/org/openapitools/api/FakeApi.java
index 60a7ef15cebd..52a89535e1ad 100644
--- a/samples/openapi3/client/petstore/spring-cloud-oas3-fakeapi/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/openapi3/client/petstore/spring-cloud-oas3-fakeapi/src/main/java/org/openapitools/api/FakeApi.java
@@ -373,7 +373,7 @@ ResponseEntity<Void> testEnumParameters(
     )
     ResponseEntity<Void> testGroupParameters(
         @NotNull @Parameter(name = "required_string_group", description = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @Parameter(name = "required_int64_group", description = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @Parameter(name = "string_group", description = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @Parameter(name = "boolean_group", description = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/openapi3/server/petstore/springboot-beanvalidation-no-nullable/src/main/java/org/openapitools/api/FakeApi.java b/samples/openapi3/server/petstore/springboot-beanvalidation-no-nullable/src/main/java/org/openapitools/api/FakeApi.java
index f4680d0dbbaa..ac1a7abb0a75 100644
--- a/samples/openapi3/server/petstore/springboot-beanvalidation-no-nullable/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/openapi3/server/petstore/springboot-beanvalidation-no-nullable/src/main/java/org/openapitools/api/FakeApi.java
@@ -426,7 +426,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @Parameter(name = "required_string_group", description = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @Parameter(name = "required_int64_group", description = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @Parameter(name = "string_group", description = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @Parameter(name = "boolean_group", description = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/openapi3/server/petstore/springboot-delegate/src/main/java/org/openapitools/api/FakeApi.java b/samples/openapi3/server/petstore/springboot-delegate/src/main/java/org/openapitools/api/FakeApi.java
index be0c8a2ba5f9..3dd29c3b7302 100644
--- a/samples/openapi3/server/petstore/springboot-delegate/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/openapi3/server/petstore/springboot-delegate/src/main/java/org/openapitools/api/FakeApi.java
@@ -394,7 +394,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @Parameter(name = "required_string_group", description = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @Parameter(name = "required_int64_group", description = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @Parameter(name = "string_group", description = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @Parameter(name = "boolean_group", description = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/openapi3/server/petstore/springboot-reactive/src/main/java/org/openapitools/api/FakeApi.java b/samples/openapi3/server/petstore/springboot-reactive/src/main/java/org/openapitools/api/FakeApi.java
index a0c82a3ceb0e..2153475713eb 100644
--- a/samples/openapi3/server/petstore/springboot-reactive/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/openapi3/server/petstore/springboot-reactive/src/main/java/org/openapitools/api/FakeApi.java
@@ -408,7 +408,7 @@ default Mono<ResponseEntity<Void>> testEnumParameters(
     )
     default Mono<ResponseEntity<Void>> testGroupParameters(
         @NotNull @Parameter(name = "required_string_group", description = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @Parameter(name = "required_int64_group", description = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @Parameter(name = "string_group", description = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @Parameter(name = "boolean_group", description = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/openapi3/server/petstore/springboot-useoptional/src/main/java/org/openapitools/api/FakeApi.java b/samples/openapi3/server/petstore/springboot-useoptional/src/main/java/org/openapitools/api/FakeApi.java
index 93c00a753ead..62080a519104 100644
--- a/samples/openapi3/server/petstore/springboot-useoptional/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/openapi3/server/petstore/springboot-useoptional/src/main/java/org/openapitools/api/FakeApi.java
@@ -426,7 +426,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @Parameter(name = "required_string_group", description = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @Parameter(name = "required_int64_group", description = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @Parameter(name = "string_group", description = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Optional<Integer> stringGroup,
         @Parameter(name = "boolean_group", description = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Optional<Boolean> booleanGroup,
diff --git a/samples/server/petstore/spring-boot-defaultInterface-unhandledException/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/spring-boot-defaultInterface-unhandledException/src/main/java/org/openapitools/api/FakeApi.java
index cffefce18123..24f3e6280443 100644
--- a/samples/server/petstore/spring-boot-defaultInterface-unhandledException/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/spring-boot-defaultInterface-unhandledException/src/main/java/org/openapitools/api/FakeApi.java
@@ -374,7 +374,7 @@ ResponseEntity<Void> testEnumParameters(
     )
     ResponseEntity<Void> testGroupParameters(
         @NotNull @Parameter(name = "required_string_group", description = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @Parameter(name = "required_int64_group", description = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @Parameter(name = "string_group", description = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @Parameter(name = "boolean_group", description = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/server/petstore/springboot-beanvalidation-no-nullable/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/springboot-beanvalidation-no-nullable/src/main/java/org/openapitools/api/FakeApi.java
index 6d706b8c5d11..60fcd0ffc147 100644
--- a/samples/server/petstore/springboot-beanvalidation-no-nullable/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/springboot-beanvalidation-no-nullable/src/main/java/org/openapitools/api/FakeApi.java
@@ -431,7 +431,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @ApiParam(value = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @ApiParam(value = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @ApiParam(value = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @ApiParam(value = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/server/petstore/springboot-beanvalidation/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/springboot-beanvalidation/src/main/java/org/openapitools/api/FakeApi.java
index 6d706b8c5d11..60fcd0ffc147 100644
--- a/samples/server/petstore/springboot-beanvalidation/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/springboot-beanvalidation/src/main/java/org/openapitools/api/FakeApi.java
@@ -431,7 +431,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @ApiParam(value = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @ApiParam(value = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @ApiParam(value = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @ApiParam(value = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/server/petstore/springboot-delegate-j8/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/springboot-delegate-j8/src/main/java/org/openapitools/api/FakeApi.java
index e716498aa68f..1aec4bb6c161 100644
--- a/samples/server/petstore/springboot-delegate-j8/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/springboot-delegate-j8/src/main/java/org/openapitools/api/FakeApi.java
@@ -399,7 +399,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @ApiParam(value = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @ApiParam(value = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @ApiParam(value = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @ApiParam(value = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/server/petstore/springboot-delegate/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/springboot-delegate/src/main/java/org/openapitools/api/FakeApi.java
index e716498aa68f..1aec4bb6c161 100644
--- a/samples/server/petstore/springboot-delegate/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/springboot-delegate/src/main/java/org/openapitools/api/FakeApi.java
@@ -399,7 +399,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @ApiParam(value = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @ApiParam(value = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @ApiParam(value = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @ApiParam(value = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/server/petstore/springboot-reactive/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/springboot-reactive/src/main/java/org/openapitools/api/FakeApi.java
index 131716a99467..c7441c800dce 100644
--- a/samples/server/petstore/springboot-reactive/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/springboot-reactive/src/main/java/org/openapitools/api/FakeApi.java
@@ -414,7 +414,7 @@ default Mono<ResponseEntity<Void>> testEnumParameters(
     )
     default Mono<ResponseEntity<Void>> testGroupParameters(
         @NotNull @ApiParam(value = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @ApiParam(value = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @ApiParam(value = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @ApiParam(value = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/server/petstore/springboot-spring-pageable-delegatePattern-without-j8/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/springboot-spring-pageable-delegatePattern-without-j8/src/main/java/org/openapitools/api/FakeApi.java
index 12db61228632..eb42b3858fb0 100644
--- a/samples/server/petstore/springboot-spring-pageable-delegatePattern-without-j8/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/springboot-spring-pageable-delegatePattern-without-j8/src/main/java/org/openapitools/api/FakeApi.java
@@ -399,7 +399,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @ApiParam(value = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @ApiParam(value = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @ApiParam(value = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @ApiParam(value = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/server/petstore/springboot-spring-pageable-delegatePattern/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/springboot-spring-pageable-delegatePattern/src/main/java/org/openapitools/api/FakeApi.java
index 12db61228632..eb42b3858fb0 100644
--- a/samples/server/petstore/springboot-spring-pageable-delegatePattern/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/springboot-spring-pageable-delegatePattern/src/main/java/org/openapitools/api/FakeApi.java
@@ -399,7 +399,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @ApiParam(value = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @ApiParam(value = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @ApiParam(value = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @ApiParam(value = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/server/petstore/springboot-spring-pageable-without-j8/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/springboot-spring-pageable-without-j8/src/main/java/org/openapitools/api/FakeApi.java
index 26c3a96c223b..b451d40c28ea 100644
--- a/samples/server/petstore/springboot-spring-pageable-without-j8/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/springboot-spring-pageable-without-j8/src/main/java/org/openapitools/api/FakeApi.java
@@ -431,7 +431,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @ApiParam(value = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @ApiParam(value = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @ApiParam(value = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @ApiParam(value = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/server/petstore/springboot-spring-pageable/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/springboot-spring-pageable/src/main/java/org/openapitools/api/FakeApi.java
index 26c3a96c223b..b451d40c28ea 100644
--- a/samples/server/petstore/springboot-spring-pageable/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/springboot-spring-pageable/src/main/java/org/openapitools/api/FakeApi.java
@@ -431,7 +431,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @ApiParam(value = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @ApiParam(value = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @ApiParam(value = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @ApiParam(value = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/server/petstore/springboot-useoptional/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/springboot-useoptional/src/main/java/org/openapitools/api/FakeApi.java
index 83342f00f497..62eb0dbc4578 100644
--- a/samples/server/petstore/springboot-useoptional/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/springboot-useoptional/src/main/java/org/openapitools/api/FakeApi.java
@@ -431,7 +431,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @ApiParam(value = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @ApiParam(value = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @ApiParam(value = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Optional<Integer> stringGroup,
         @ApiParam(value = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Optional<Boolean> booleanGroup,
diff --git a/samples/server/petstore/springboot-virtualan/src/main/java/org/openapitools/virtualan/api/FakeApi.java b/samples/server/petstore/springboot-virtualan/src/main/java/org/openapitools/virtualan/api/FakeApi.java
index 3537e3eebde1..1f3e3dd529f8 100644
--- a/samples/server/petstore/springboot-virtualan/src/main/java/org/openapitools/virtualan/api/FakeApi.java
+++ b/samples/server/petstore/springboot-virtualan/src/main/java/org/openapitools/virtualan/api/FakeApi.java
@@ -440,7 +440,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @Parameter(name = "required_string_group", description = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @Parameter(name = "required_boolean_group", description = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @Parameter(name = "required_int64_group", description = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @Parameter(name = "string_group", description = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @Parameter(name = "boolean_group", description = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,
diff --git a/samples/server/petstore/springboot/src/main/java/org/openapitools/api/FakeApi.java b/samples/server/petstore/springboot/src/main/java/org/openapitools/api/FakeApi.java
index 6d706b8c5d11..60fcd0ffc147 100644
--- a/samples/server/petstore/springboot/src/main/java/org/openapitools/api/FakeApi.java
+++ b/samples/server/petstore/springboot/src/main/java/org/openapitools/api/FakeApi.java
@@ -431,7 +431,7 @@ default ResponseEntity<Void> testEnumParameters(
     )
     default ResponseEntity<Void> testGroupParameters(
         @NotNull @ApiParam(value = "Required String in group parameters", required = true) @Valid @RequestParam(value = "required_string_group", required = true) Integer requiredStringGroup,
-        @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
+        @NotNull @ApiParam(value = "Required Boolean in group parameters", required = true) @RequestHeader(value = "required_boolean_group", required = true) Boolean requiredBooleanGroup,
         @NotNull @ApiParam(value = "Required Integer in group parameters", required = true) @Valid @RequestParam(value = "required_int64_group", required = true) Long requiredInt64Group,
         @ApiParam(value = "String in group parameters") @Valid @RequestParam(value = "string_group", required = false) Integer stringGroup,
         @ApiParam(value = "Boolean in group parameters") @RequestHeader(value = "boolean_group", required = false) Boolean booleanGroup,