diff --git a/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java b/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java
index c86e95a93a..75a7a1fc3b 100644
--- a/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.java
+++ b/spring-test/src/main/java/org/springframework/mock/web/MockHttpServletResponse.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.
@@ -24,11 +24,11 @@ import java.io.PrintWriter;
 import java.io.UnsupportedEncodingException;
 import java.io.Writer;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
-import java.util.Set;
 import javax.servlet.ServletOutputStream;
 import javax.servlet.http.Cookie;
 import javax.servlet.http.HttpServletResponse;
@@ -56,6 +56,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 
 	private static final String LOCATION_HEADER = "Location";
 
+
 	//---------------------------------------------------------------------
 	// ServletResponse properties
 	//---------------------------------------------------------------------
@@ -145,7 +146,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	private void updateContentTypeHeader() {
 		if (this.contentType != null) {
 			StringBuilder sb = new StringBuilder(this.contentType);
-			if (this.contentType.toLowerCase().indexOf(CHARSET_PREFIX) == -1 && this.charset) {
+			if (!this.contentType.toLowerCase().contains(CHARSET_PREFIX) && this.charset) {
 				sb.append(";").append(CHARSET_PREFIX).append(this.characterEncoding);
 			}
 			doAddHeaderValue(CONTENT_TYPE_HEADER, sb.toString(), true);
@@ -299,7 +300,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	 * <p>As of Servlet 3.0, this method is also defined HttpServletResponse.
 	 * @return the {@code Set} of header name {@code Strings}, or an empty {@code Set} if none
 	 */
-	public Set<String> getHeaderNames() {
+	public Collection<String> getHeaderNames() {
 		return this.headers.keySet();
 	}
 
diff --git a/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java b/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java
index c16f7cab9e..867b86ad90 100644
--- a/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.java
+++ b/spring-test/src/test/java/org/springframework/mock/web/MockHttpServletResponseTests.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.
@@ -16,18 +16,17 @@
 
 package org.springframework.mock.web;
 
-import static org.junit.Assert.*;
-
 import java.io.IOException;
 import java.util.Arrays;
-import java.util.Set;
-
+import java.util.Collection;
 import javax.servlet.http.HttpServletResponse;
 
 import org.junit.Test;
 
 import org.springframework.web.util.WebUtils;
 
+import static org.junit.Assert.*;
+
 /**
  * Unit tests for {@link MockHttpServletResponse}.
  *
@@ -127,7 +126,7 @@ public class MockHttpServletResponseTests {
 	public void httpHeaderNameCasingIsPreserved() throws Exception {
 		final String headerName = "Header1";
 		response.addHeader(headerName, "value1");
-		Set<String> responseHeaders = response.getHeaderNames();
+		Collection<String> responseHeaders = response.getHeaderNames();
 		assertNotNull(responseHeaders);
 		assertEquals(1, responseHeaders.size());
 		assertEquals("HTTP header casing not being preserved", headerName, responseHeaders.iterator().next());
diff --git a/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.java b/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.java
index 6f52ab8e3e..990026770d 100644
--- a/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.java
+++ b/spring-web/src/test/java/org/springframework/mock/web/test/MockHttpServletResponse.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.
@@ -24,11 +24,11 @@ import java.io.PrintWriter;
 import java.io.UnsupportedEncodingException;
 import java.io.Writer;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
-import java.util.Set;
 import javax.servlet.ServletOutputStream;
 import javax.servlet.http.Cookie;
 import javax.servlet.http.HttpServletResponse;
@@ -38,11 +38,9 @@ import org.springframework.util.LinkedCaseInsensitiveMap;
 import org.springframework.web.util.WebUtils;
 
 /**
- * Mock implementation of the {@link javax.servlet.http.HttpServletResponse}
- * interface. Supports the Servlet 3.0 API level
+ * Mock implementation of the {@link javax.servlet.http.HttpServletResponse} interface.
  *
- * <p>Used for testing the web framework; also useful for testing
- * application controllers.
+ * <p>Compatible with Servlet 2.5 as well as Servlet 3.0.
  *
  * @author Juergen Hoeller
  * @author Rod Johnson
@@ -58,6 +56,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 
 	private static final String LOCATION_HEADER = "Location";
 
+
 	//---------------------------------------------------------------------
 	// ServletResponse properties
 	//---------------------------------------------------------------------
@@ -148,7 +147,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	private void updateContentTypeHeader() {
 		if (this.contentType != null) {
 			StringBuilder sb = new StringBuilder(this.contentType);
-			if (this.contentType.toLowerCase().indexOf(CHARSET_PREFIX) == -1 && this.charset) {
+			if (!this.contentType.toLowerCase().contains(CHARSET_PREFIX) && this.charset) {
 				sb.append(";").append(CHARSET_PREFIX).append(this.characterEncoding);
 			}
 			doAddHeaderValue(CONTENT_TYPE_HEADER, sb.toString(), true);
@@ -319,7 +318,7 @@ public class MockHttpServletResponse implements HttpServletResponse {
 	 * @return the {@code Set} of header name {@code Strings}, or an empty {@code Set} if none
 	 */
 	@Override
-	public Set<String> getHeaderNames() {
+	public Collection<String> getHeaderNames() {
 		return this.headers.keySet();
 	}