diff --git a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompiler.kt b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompiler.kt
index c72cb295385..682139f57e3 100644
--- a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompiler.kt
+++ b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompiler.kt
@@ -1,5 +1,6 @@
 package com.apollographql.apollo.compiler
 
+import com.apollographql.apollo.annotations.ApolloExperimental
 import com.apollographql.apollo.ast.DeprecatedUsage
 import com.apollographql.apollo.ast.DifferentShape
 import com.apollographql.apollo.ast.DirectiveRedefinition
@@ -605,6 +606,7 @@ fun Collection<File>.toInputFiles(): List<InputFile> = map { InputFile(it, "") }
 
 internal fun <T> T.maybeTransform(transform: Transform<T>?) = transform?.transform(this) ?: this
 
+@ApolloExperimental
 interface LayoutFactory {
   fun create(codegenSchema: CodegenSchema): SchemaAndOperationsLayout?
 }
diff --git a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPlugin.kt b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPlugin.kt
index a78b7af651a..6493d578751 100644
--- a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPlugin.kt
+++ b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPlugin.kt
@@ -160,6 +160,7 @@ interface DocumentTransform {
  * This is not a kotlin function type because this might be used in environment where those types are
  * relocated and might fail to load at runtime. For an example, in a Gradle plugin.
  */
+@ApolloExperimental
 interface Transform<T> {
   /**
    * Transforms the given input into an output of the same type
diff --git a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPluginEnvironment.kt b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPluginEnvironment.kt
index 37361b0aaa9..67e939229f6 100644
--- a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPluginEnvironment.kt
+++ b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPluginEnvironment.kt
@@ -1,11 +1,8 @@
 package com.apollographql.apollo.compiler
 
-import com.apollographql.apollo.annotations.ApolloExperimental
-
 /**
  * [ApolloCompilerPluginEnvironment] contains the environment where the Apollo compiler is run.
  */
-@ApolloExperimental
 class ApolloCompilerPluginEnvironment(
     /**
      * @see [ApolloCompilerPluginValue]
@@ -30,5 +27,4 @@ class ApolloCompilerPluginEnvironment(
  * - [List]
  * - [Map]
  */
-@ApolloExperimental
 typealias ApolloCompilerPluginValue = Any?
\ No newline at end of file
diff --git a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPluginLogger.kt b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPluginLogger.kt
index 5a5151e8cdb..c53bbbf06b4 100644
--- a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPluginLogger.kt
+++ b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/ApolloCompilerPluginLogger.kt
@@ -1,13 +1,10 @@
 package com.apollographql.apollo.compiler
 
-import com.apollographql.apollo.annotations.ApolloExperimental
-
 /**
  * [ApolloCompilerPluginLogger] allows logging from the context of the Apollo compiler.
  *
  * Typically, the Apollo compiler is run from an isolated classloader and cannot use the Gradle logging functions but can respect the logging level set by the user.
  */
-@ApolloExperimental
 interface ApolloCompilerPluginLogger {
   fun logging(message: String)
   fun info(message: String)
diff --git a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/codegen/SchemaAndOperationsLayout.kt b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/codegen/SchemaAndOperationsLayout.kt
index f1c5059ea60..d8e731d314a 100644
--- a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/codegen/SchemaAndOperationsLayout.kt
+++ b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/codegen/SchemaAndOperationsLayout.kt
@@ -1,10 +1,14 @@
 package com.apollographql.apollo.compiler.codegen
 
+import com.apollographql.apollo.annotations.ApolloExperimental
+
+@ApolloExperimental
 interface CommonLayout {
   fun className(name: String): String
   fun propertyName(name: String): String
 }
 
+@ApolloExperimental
 interface SchemaLayout : CommonLayout {
   fun schemaPackageName(): String
   fun schemaTypeName(schemaTypeName: String): String
@@ -13,10 +17,12 @@ interface SchemaLayout : CommonLayout {
   fun paginationName(): String
 }
 
+@ApolloExperimental
 interface OperationsLayout: CommonLayout {
   fun executableDocumentPackageName(filePath: String?): String
   fun operationName(name: String, capitalizedOperationType: String): String
   fun fragmentName(name: String): String
 }
 
+@ApolloExperimental
 interface SchemaAndOperationsLayout : SchemaLayout, OperationsLayout
diff --git a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/entrypoints.kt b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/entrypoints.kt
index f2042f6b43c..4c279034daa 100644
--- a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/entrypoints.kt
+++ b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/entrypoints.kt
@@ -107,7 +107,7 @@ class EntryPoints {
     ).writeTo(outputDir, true, metadataOutputFile)
 
     if (upstreamCodegenMetadata.isEmpty()) {
-      registry.extraCodeGenerator().generate(codegenSchema.schema.toGQLDocument(), outputDir)
+      registry.schemaCodeGenerator().generate(codegenSchema.schema.toGQLDocument(), outputDir)
     }
   }
 
@@ -156,7 +156,7 @@ class EntryPoints {
         operationManifestFile = operationManifestFile,
     ).writeTo(outputDir, true, null)
 
-    registry.extraCodeGenerator().generate(codegenSchema.schema.toGQLDocument(), outputDir)
+    registry.schemaCodeGenerator().generate(codegenSchema.schema.toGQLDocument(), outputDir)
   }
 }
 
diff --git a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/internal/DefaultApolloCompilerRegistry.kt b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/internal/DefaultApolloCompilerRegistry.kt
index 140b88b66a7..982cc832b36 100644
--- a/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/internal/DefaultApolloCompilerRegistry.kt
+++ b/libraries/apollo-compiler/src/main/kotlin/com/apollographql/apollo/compiler/internal/DefaultApolloCompilerRegistry.kt
@@ -240,7 +240,7 @@ internal class DefaultApolloCompilerRegistry : ApolloCompilerRegistry {
     }
   }
 
-  fun extraCodeGenerator(): SchemaCodeGenerator {
+  fun schemaCodeGenerator(): SchemaCodeGenerator {
     return SchemaCodeGenerator { document, outputDirectory ->
       extraSchemaCodeGenerators.forEach {
         it.generate(document, outputDirectory)
diff --git a/libraries/apollo-compiler/src/test/kotlin/com/apollographql/apollo/compiler/keyfields/KeyFieldsTest.kt b/libraries/apollo-compiler/src/test/kotlin/com/apollographql/apollo/compiler/keyfields/KeyFieldsTest.kt
index 1673a1fb0f6..02a945d76dc 100644
--- a/libraries/apollo-compiler/src/test/kotlin/com/apollographql/apollo/compiler/keyfields/KeyFieldsTest.kt
+++ b/libraries/apollo-compiler/src/test/kotlin/com/apollographql/apollo/compiler/keyfields/KeyFieldsTest.kt
@@ -2,16 +2,49 @@ package com.apollographql.apollo.compiler.keyfields
 
 import com.apollographql.apollo.ast.GQLDocument
 import com.apollographql.apollo.ast.GQLExecutableDefinition
+import com.apollographql.apollo.ast.GQLFragmentDefinition
+import com.apollographql.apollo.ast.GQLOperationDefinition
 import com.apollographql.apollo.ast.parseAsGQLDocument
 import com.apollographql.apollo.ast.toGQLDocument
 import com.apollographql.apollo.ast.validateAsSchemaAndAddApolloDefinition
+import com.apollographql.apollo.compiler.internal.ApolloExecutableDocumentTransform
+import com.apollographql.apollo.compiler.internal.checkKeyFields
 import okio.Path.Companion.toPath
 import kotlin.test.Test
 import kotlin.test.assertContains
 import kotlin.test.assertEquals
 import kotlin.test.assertTrue
+import kotlin.test.fail
 
 class KeyFieldsTest {
+  @Test
+  fun testAddRequiredFields() {
+    val schema = "src/test/kotlin/com/apollographql/apollo/compiler/keyfields/schema.graphqls"
+        .toPath()
+        .toGQLDocument()
+        .validateAsSchemaAndAddApolloDefinition()
+        .getOrThrow()
+
+    val document = "src/test/kotlin/com/apollographql/apollo/compiler/keyfields/operations.graphql".toPath()
+        .toGQLDocument()
+    val definitions = document.definitions
+
+    val operation = definitions
+        .filterIsInstance<GQLOperationDefinition>()
+        .first()
+
+    try {
+      checkKeyFields(operation, schema, emptyMap())
+      fail("an exception was expected")
+    } catch (e: Exception) {
+      assertTrue(e.message?.contains("are not queried") == true)
+    }
+
+    // The document contains a single operation
+    val operationWithKeyFields = ApolloExecutableDocumentTransform("ifFragments", true).transform(schema, document, emptyList()).definitions.single() as GQLOperationDefinition
+    checkKeyFields(operationWithKeyFields, schema, emptyMap())
+  }
+
   @Test
   fun testExtendInterfaceTypePolicyDirective() {
     val schema = "src/test/kotlin/com/apollographql/apollo/compiler/keyfields/extendsSchema.graphqls"