diff --git a/spring-test/src/main/java/org/springframework/test/web/servlet/setup/ConfigurableMockMvcBuilder.java b/spring-test/src/main/java/org/springframework/test/web/servlet/setup/ConfigurableMockMvcBuilder.java
index 145dccc8a3..45b9f05d04 100644
--- a/spring-test/src/main/java/org/springframework/test/web/servlet/setup/ConfigurableMockMvcBuilder.java
+++ b/spring-test/src/main/java/org/springframework/test/web/servlet/setup/ConfigurableMockMvcBuilder.java
@@ -93,7 +93,7 @@ public interface ConfigurableMockMvcBuilder<B extends ConfigurableMockMvcBuilder
 	 * @since 5.3.10
 	 */
 	default <T extends B> T defaultResponseCharacterEncoding(Charset defaultResponseCharacterEncoding) {
-		throw new UnsupportedOperationException();
+		throw new UnsupportedOperationException("defaultResponseCharacterEncoding is not supported by this MockMvcBuilder");
 	}
 
 	/**