diff --git a/src/main/kotlin/graphql/kickstart/tools/SchemaClassScanner.kt b/src/main/kotlin/graphql/kickstart/tools/SchemaClassScanner.kt
index e91e3e2c..b327b7e4 100644
--- a/src/main/kotlin/graphql/kickstart/tools/SchemaClassScanner.kt
+++ b/src/main/kotlin/graphql/kickstart/tools/SchemaClassScanner.kt
@@ -91,15 +91,14 @@ internal class SchemaClassScanner(
             do {
                 val unusedDefinitions = (definitionsByName.values - (dictionary.keys.toSet() + unvalidatedTypes))
                     .filter { definition -> definition.name != "PageInfo" }
-                    .filterIsInstance<ObjectTypeDefinition>().distinct()
+                    .filter { isCompositeOrEnumType(it) }
+                    .distinct()
 
                 if (unusedDefinitions.isEmpty()) {
                     break
                 }
 
-                val unusedDefinition = unusedDefinitions.first()
-
-                handleDictionaryTypes(listOf(unusedDefinition)) { "Object type '${it.name}' is unused and includeUnusedTypes is true. Please pass a class for type '${it.name}' in the parser's dictionary." }
+                handleDictionaryTypes(unusedDefinitions) { "Type '${it.name}' is unused and includeUnusedTypes is true. Please pass a class for type '${it.name}' in the parser's dictionary." }
             } while (scanQueue())
         }
 
@@ -108,6 +107,10 @@ internal class SchemaClassScanner(
         return validateAndCreateResult(rootTypeHolder)
     }
 
+    private fun isCompositeOrEnumType(definition: TypeDefinition<*>): Boolean {
+        return definition is ObjectTypeDefinition || definition is InterfaceTypeDefinition || definition is UnionTypeDefinition || definition is EnumTypeDefinition
+    }
+
     private fun scanQueue(): Boolean {
         if (queue.isEmpty()) {
             return false
diff --git a/src/test/kotlin/graphql/kickstart/tools/SchemaClassScannerTest.kt b/src/test/kotlin/graphql/kickstart/tools/SchemaClassScannerTest.kt
index 9dff7011..e7a2f758 100644
--- a/src/test/kotlin/graphql/kickstart/tools/SchemaClassScannerTest.kt
+++ b/src/test/kotlin/graphql/kickstart/tools/SchemaClassScannerTest.kt
@@ -526,12 +526,19 @@ class SchemaClassScannerTest {
                 type Implementation implements SomeInterface {
                     value: String
                 }
+                
+                union SomeUnion = Unused | Implementation
+                
+                enum SomeEnum {
+                   A
+                   B
+                }
                 """)
             .resolvers(object : GraphQLQueryResolver {
                 fun whatever(): Whatever? = null
             })
             .options(SchemaParserOptions.newOptions().includeUnusedTypes(true).build())
-            .dictionary(Unused::class, Implementation::class)
+            .dictionary(Unused::class, Implementation::class, SomeInterface::class, SomeUnion::class, SomeEnum::class)
             .build()
             .makeExecutableSchema()
 
diff --git a/src/test/kotlin/graphql/kickstart/tools/TestInterfaces.kt b/src/test/kotlin/graphql/kickstart/tools/TestInterfaces.kt
index 17a22a91..52e2ff54 100644
--- a/src/test/kotlin/graphql/kickstart/tools/TestInterfaces.kt
+++ b/src/test/kotlin/graphql/kickstart/tools/TestInterfaces.kt
@@ -14,3 +14,10 @@ interface SomeInterface {
     fun getValue(): String?
 }
 
+interface SomeUnion
+
+enum class SomeEnum {
+    A,
+    B
+}
+