diff --git a/modules/openapi-generator/src/main/resources/Java/beanValidationQueryParams.mustache b/modules/openapi-generator/src/main/resources/Java/beanValidationQueryParams.mustache
index c4ff01d7e55..0f99bffde09 100644
--- a/modules/openapi-generator/src/main/resources/Java/beanValidationQueryParams.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/beanValidationQueryParams.mustache
@@ -1 +1 @@
-{{#required}} @NotNull{{/required}}{{>beanValidationCore}}
\ No newline at end of file
+{{#required}} @NotNull {{/required}}{{>beanValidationCore}}
\ No newline at end of file
diff --git a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java
index c0bf2b4dc2b..99892f884be 100644
--- a/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java
+++ b/modules/openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java
@@ -37,6 +37,7 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Optional;
+import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -53,8 +54,10 @@ import org.openapitools.codegen.CodegenSecurity;
 import org.openapitools.codegen.DefaultGenerator;
 import org.openapitools.codegen.TestUtils;
 import org.openapitools.codegen.config.CodegenConfigurator;
+import org.openapitools.codegen.java.assertions.JavaFileAssert;
 import org.openapitools.codegen.languages.AbstractJavaCodegen;
 import org.openapitools.codegen.languages.JavaClientCodegen;
+import org.openapitools.codegen.languages.features.BeanValidationFeatures;
 import org.openapitools.codegen.languages.features.CXFServerFeatures;
 import org.testng.Assert;
 import org.testng.annotations.Ignore;
@@ -1409,4 +1412,36 @@ public class JavaClientCodegenTest {
         TestUtils.assertExtraAnnotationFiles(outputPath + "/src/main/java/org/openapitools/client/model");
 
     }
+
+    /**
+     * See https://github.com/OpenAPITools/openapi-generator/issues/11340
+     */
+    @Test
+    public void testReferencedHeader2() throws Exception {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+        Map<String, Object> additionalProperties = new HashMap<>();
+        additionalProperties.put(BeanValidationFeatures.USE_BEANVALIDATION, "true");
+        final CodegenConfigurator configurator = new CodegenConfigurator().setGeneratorName("java")
+                .setAdditionalProperties(additionalProperties)
+                .setInputSpec("src/test/resources/3_0/issue-11340.yaml")
+                .setOutputDir(output.getAbsolutePath()
+                        .replace("\\", "/"));
+
+        final ClientOptInput clientOptInput = configurator.toClientOptInput();
+        DefaultGenerator generator = new DefaultGenerator();
+
+        Map<String, File> files = generator.opts(clientOptInput).generate().stream()
+                .collect(Collectors.toMap(File::getName, Function.identity()));
+
+        JavaFileAssert.assertThat(files.get("DefaultApi.java"))
+                .assertMethod("operationWithHttpInfo")
+                    .hasParameter("requestBody")
+                    .assertParameterAnnotations()
+                    .containsWithName("NotNull")
+                .toParameter().toMethod()
+                    .hasParameter("xNonNullHeaderParameter")
+                    .assertParameterAnnotations()
+                    .containsWithName("NotNull");
+    }
 }
diff --git a/modules/openapi-generator/src/test/resources/3_0/issue-11340.yaml b/modules/openapi-generator/src/test/resources/3_0/issue-11340.yaml
new file mode 100644
index 00000000000..167a82b12c2
--- /dev/null
+++ b/modules/openapi-generator/src/test/resources/3_0/issue-11340.yaml
@@ -0,0 +1,28 @@
+openapi: "3.0.3"
+info:
+  title: Issue 11340 - Bean Validation Breaks Generated Java Code
+  version: "1.0.2"
+  description: With Bean Validation @NotNull and type of parameter must be separated by space.
+paths:
+  /configuration:
+    put:
+      operationId: operation
+      description: Operation with required header and required request body
+      parameters:
+        - in: header
+          name: x-non-null-header-parameter
+          schema:
+            type: string
+          required: true
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              minProperties: 1
+              additionalProperties:
+                type: object
+      responses:
+        '200':
+          description: OK