diff --git a/spring-test/src/main/java/org/springframework/mock/web/MockHttpSession.java b/spring-test/src/main/java/org/springframework/mock/web/MockHttpSession.java
index 3b30a83e32b..39d771b2f5d 100644
--- a/spring-test/src/main/java/org/springframework/mock/web/MockHttpSession.java
+++ b/spring-test/src/main/java/org/springframework/mock/web/MockHttpSession.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 the original author or authors.
+ * Copyright 2002-2012 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.
@@ -39,6 +39,7 @@ import org.springframework.util.Assert;
  * @author Juergen Hoeller
  * @author Rod Johnson
  * @author Mark Fisher
+ * @author Sam Brannen
  * @since 1.0.2
  */
 @SuppressWarnings("deprecation")
@@ -186,7 +187,17 @@ public class MockHttpSession implements HttpSession {
 		}
 	}
 
+	/**
+	 * Invalidates this session then unbinds any objects bound to it.
+	 *
+	 * @throws IllegalStateException if this method is called on an already invalidated session
+	 */
 	public void invalidate() {
+		if (this.invalid) {
+			throw new IllegalStateException("The session has already been invalidated");
+		}
+
+		// else
 		this.invalid = true;
 		clearAttributes();
 	}
diff --git a/spring-test/src/test/java/org/springframework/mock/web/MockHttpSessionTests.java b/spring-test/src/test/java/org/springframework/mock/web/MockHttpSessionTests.java
new file mode 100644
index 00000000000..0379ea78d0e
--- /dev/null
+++ b/spring-test/src/test/java/org/springframework/mock/web/MockHttpSessionTests.java
@@ -0,0 +1,47 @@
+/*
+ * Copyright 2002-2012 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 the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.mock.web;
+
+import static org.junit.Assert.*;
+
+import org.junit.Test;
+
+/**
+ * Unit tests for {@link MockHttpSession}.
+ *
+ * @author Sam Brannen
+ * @since 3.2
+ */
+public class MockHttpSessionTests {
+
+	private MockHttpSession session = new MockHttpSession();
+
+
+	@Test
+	public void invalidateOnce() {
+		assertFalse(session.isInvalid());
+		session.invalidate();
+		assertTrue(session.isInvalid());
+	}
+
+	@Test(expected = IllegalStateException.class)
+	public void invalidateTwice() {
+		session.invalidate();
+		session.invalidate();
+	}
+
+}