diff --git a/libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo/ast/internal/definitions.kt b/libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo/ast/internal/definitions.kt
index e65c5dcc04a..a5e8c15e4ef 100644
--- a/libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo/ast/internal/definitions.kt
+++ b/libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo/ast/internal/definitions.kt
@@ -310,7 +310,7 @@ internal val builtinsDefinitionsStr = """
   directive @include(if: Boolean!) on FIELD | FRAGMENT_SPREAD | INLINE_FRAGMENT
 
   directive @deprecated(
-    reason: String = "No longer supported"
+    reason: String! = "No longer supported"
   ) on FIELD_DEFINITION | ARGUMENT_DEFINITION | INPUT_FIELD_DEFINITION | ENUM_VALUE
 
   directive @defer(
diff --git a/libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo/ast/introspection/introspection_reader.kt b/libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo/ast/introspection/introspection_reader.kt
index 9bbe206874e..a337546f163 100644
--- a/libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo/ast/introspection/introspection_reader.kt
+++ b/libraries/apollo-ast/src/commonMain/kotlin/com/apollographql/apollo/ast/introspection/introspection_reader.kt
@@ -369,16 +369,11 @@ private class GQLDocumentBuilder(private val introspectionSchema: IntrospectionS
   }
 
   /**
-   * This assumes the case where `deprecationReason == null && isDeprecated` is not valid
-   * which is unclear from reading the spec as the below seems allowed:
+   * This assumes the case where `deprecationReason == null && isDeprecated` is not valid.
    *
-   * ```
-   * type Query {
-   *   foo: Int @deprecated(reason: null)
-   * }
-   * ```
+   * See https://github.com/graphql/graphql-spec/pull/1040
    *
-   * If there are legit use cases for `@deprecated(reason: null)` we should update this function
+   * If a legacy schema contains `@deprecated(reason: null)`, the field appears as non-deprecated.
    */
   fun makeDirectives(deprecationReason: String?): List<GQLDirective> {
     if (deprecationReason == null) {
diff --git a/libraries/apollo-ast/test-fixtures/sdl/type_redefinitions.expected b/libraries/apollo-ast/test-fixtures/sdl/type_redefinitions.expected
index aaa7e6dcc5b..3eb483ef630 100644
--- a/libraries/apollo-ast/test-fixtures/sdl/type_redefinitions.expected
+++ b/libraries/apollo-ast/test-fixtures/sdl/type_redefinitions.expected
@@ -150,7 +150,7 @@ directive @skip (if: Boolean!) on FIELD|FRAGMENT_SPREAD|INLINE_FRAGMENT
 
 directive @include (if: Boolean!) on FIELD|FRAGMENT_SPREAD|INLINE_FRAGMENT
 
-directive @deprecated (reason: String = "No longer supported") on FIELD_DEFINITION|ARGUMENT_DEFINITION|INPUT_FIELD_DEFINITION|ENUM_VALUE
+directive @deprecated (reason: String! = "No longer supported") on FIELD_DEFINITION|ARGUMENT_DEFINITION|INPUT_FIELD_DEFINITION|ENUM_VALUE
 
 directive @defer (label: String, if: Boolean! = true) on FRAGMENT_SPREAD|INLINE_FRAGMENT
 
diff --git a/tests/sample-server/graphql/schema.graphqls b/tests/sample-server/graphql/schema.graphqls
index 2ee11d415bb..3a82ef9889b 100644
--- a/tests/sample-server/graphql/schema.graphqls
+++ b/tests/sample-server/graphql/schema.graphqls
@@ -190,7 +190,7 @@ directive @skip (if: Boolean!) on FIELD|FRAGMENT_SPREAD|INLINE_FRAGMENT
 
 directive @include (if: Boolean!) on FIELD|FRAGMENT_SPREAD|INLINE_FRAGMENT
 
-directive @deprecated (reason: String = "No longer supported") on FIELD_DEFINITION|ARGUMENT_DEFINITION|INPUT_FIELD_DEFINITION|ENUM_VALUE
+directive @deprecated (reason: String! = "No longer supported") on FIELD_DEFINITION|ARGUMENT_DEFINITION|INPUT_FIELD_DEFINITION|ENUM_VALUE
 
 directive @defer (label: String, if: Boolean! = true) on FRAGMENT_SPREAD|INLINE_FRAGMENT