diff --git a/spring-core/src/main/java/org/springframework/util/Assert.java b/spring-core/src/main/java/org/springframework/util/Assert.java
index 05c1c4babe..193d461a05 100644
--- a/spring-core/src/main/java/org/springframework/util/Assert.java
+++ b/spring-core/src/main/java/org/springframework/util/Assert.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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. You may obtain a copy of
@@ -334,8 +334,9 @@ public abstract class Assert {
 	public static void isInstanceOf(Class type, Object obj, String message) {
 		notNull(type, "Type to check against must not be null");
 		if (!type.isInstance(obj)) {
-			throw new IllegalArgumentException(message +
-					". Object of class [" + (obj != null ? obj.getClass().getName() : "null") +
+			throw new IllegalArgumentException(
+					(StringUtils.hasLength(message) ? message + " " : "") +
+					"Object of class [" + (obj != null ? obj.getClass().getName() : "null") +
 					"] must be an instance of " + type);
 		}
 	}
diff --git a/spring-core/src/test/java/org/springframework/util/AssertTests.java b/spring-core/src/test/java/org/springframework/util/AssertTests.java
index 744b492f61..0dfe86f1dc 100644
--- a/spring-core/src/test/java/org/springframework/util/AssertTests.java
+++ b/spring-core/src/test/java/org/springframework/util/AssertTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2013 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.
@@ -24,7 +24,9 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 
 /**
  * Unit tests for the {@link Assert} class.
@@ -36,6 +38,9 @@ import org.junit.Test;
  */
 public class AssertTests {
 
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
 	@Test(expected = IllegalArgumentException.class)
 	public void instanceOf() {
 		final Set<?> set = new HashSet<Object>();
@@ -43,6 +48,22 @@ public class AssertTests {
 		Assert.isInstanceOf(HashMap.class, set);
 	}
 
+	@Test
+	public void instanceOfNoMessage() throws Exception {
+		thrown.expect(IllegalArgumentException.class);
+		thrown.expectMessage("Object of class [java.lang.Object] must be an instance " +
+				"of interface java.util.Set");
+		Assert.isInstanceOf(Set.class, new Object(), null);
+	}
+
+	@Test
+	public void instanceOfMessage() throws Exception {
+		thrown.expect(IllegalArgumentException.class);
+		thrown.expectMessage("Custom message. Object of class [java.lang.Object] must " +
+				"be an instance of interface java.util.Set");
+		Assert.isInstanceOf(Set.class, new Object(), "Custom message.");
+	}
+
 	@Test
 	public void isNullDoesNotThrowExceptionIfArgumentIsNullWithMessage() {
 		Assert.isNull(null, "Bla");