diff --git a/spring-test/src/main/java/org/springframework/mock/web/MockPart.java b/spring-test/src/main/java/org/springframework/mock/web/MockPart.java
index 171cc35b4baf6c670cc1eebf75681b5c9345efa8..7a92bfd56c2c384898ad359e18923a13587b2920 100644
--- a/spring-test/src/main/java/org/springframework/mock/web/MockPart.java
+++ b/spring-test/src/main/java/org/springframework/mock/web/MockPart.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -62,7 +62,7 @@ public class MockPart implements Part {
 	 * @see #getHeaders()
 	 */
 	public MockPart(String name, @Nullable String filename, @Nullable byte[] content) {
-		Assert.hasLength(name, "Name must not be null");
+		Assert.hasLength(name, "'name' must not be empty");
 		this.name = name;
 		this.filename = filename;
 		this.content = (content != null ? content : new byte[0]);
diff --git a/spring-web/src/test/java/org/springframework/mock/web/test/MockPart.java b/spring-web/src/test/java/org/springframework/mock/web/test/MockPart.java
index 98e093dfe0cd79f617f5c28a0fc1ee47bcbf9f71..a5429b3847a52e41117b03a825348c3063187d6c 100644
--- a/spring-web/src/test/java/org/springframework/mock/web/test/MockPart.java
+++ b/spring-web/src/test/java/org/springframework/mock/web/test/MockPart.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -60,7 +60,7 @@ public class MockPart implements Part {
 	 * @see #getHeaders()
 	 */
 	public MockPart(String name, String filename, byte[] content) {
-		Assert.hasLength(name, "Name must not be null");
+		Assert.hasLength(name, "'name' must not be empty");
 		this.name = name;
 		this.filename = filename;
 		this.content = (content != null ? content : new byte[0]);