diff --git a/spring-core/src/main/java/org/springframework/aot/generate/GeneratedFiles.java b/spring-core/src/main/java/org/springframework/aot/generate/GeneratedFiles.java
index 411ec8b46baf..bd6ec60ae27c 100644
--- a/spring-core/src/main/java/org/springframework/aot/generate/GeneratedFiles.java
+++ b/spring-core/src/main/java/org/springframework/aot/generate/GeneratedFiles.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -161,7 +161,8 @@ default void addFile(Kind kind, String path, ThrowingConsumer<Appendable> conten
 
 	private static String getClassNamePath(String className) {
 		Assert.hasLength(className, "'className' must not be empty");
-		Assert.isTrue(isJavaIdentifier(className), "'className' must be a valid identifier");
+		Assert.isTrue(isJavaIdentifier(className),
+				"'className' must be a valid identifier, got '" + className + "'");
 		return ClassUtils.convertClassNameToResourcePath(className) + ".java";
 	}
 
diff --git a/spring-core/src/test/java/org/springframework/aot/generate/GeneratedFilesTests.java b/spring-core/src/test/java/org/springframework/aot/generate/GeneratedFilesTests.java
index 9f1f68ef3097..0eeb510490e9 100644
--- a/spring-core/src/test/java/org/springframework/aot/generate/GeneratedFilesTests.java
+++ b/spring-core/src/test/java/org/springframework/aot/generate/GeneratedFilesTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -78,7 +78,7 @@ void addSourceFileWithCharSequenceWhenClassNameIsInvalidThrowsException() {
 		assertThatIllegalArgumentException()
 				.isThrownBy(() -> this.generatedFiles
 						.addSourceFile("com/example/HelloWorld.java", "{}"))
-				.withMessage("'className' must be a valid identifier");
+				.withMessage("'className' must be a valid identifier, got 'com/example/HelloWorld.java'");
 	}
 
 	@Test