diff --git a/src/components/org/apache/jmeter/assertions/ResponseAssertion.java b/src/components/org/apache/jmeter/assertions/ResponseAssertion.java
index cd1e35efac..80a3ffc541 100644
--- a/src/components/org/apache/jmeter/assertions/ResponseAssertion.java
+++ b/src/components/org/apache/jmeter/assertions/ResponseAssertion.java
@@ -19,6 +19,7 @@
 package org.apache.jmeter.assertions;
 
 import java.io.Serializable;
+import java.net.URL;
 import java.util.ArrayList;
 
 import org.apache.jmeter.samplers.SampleResult;
@@ -276,9 +277,9 @@ public class ResponseAssertion extends AbstractTestElement implements Serializab
      *            an instance of SampleResult
      * @return an instance of AssertionResult
      */
-    AssertionResult evaluateResponse(SampleResult response) {
+    private AssertionResult evaluateResponse(SampleResult response) {
         boolean pass = true;
-        boolean not = (NOT & getTestType()) > 0;
+        boolean notTest = (NOT & getTestType()) > 0;
         AssertionResult result = new AssertionResult(getName());
         String toCheck = ""; // The string to check (Url or data)
 
@@ -296,26 +297,30 @@ public class ResponseAssertion extends AbstractTestElement implements Serializab
         } else if (isTestFieldResponseHeaders()) {
             toCheck = response.getResponseHeaders();
         } else { // Assume it is the URL
-            toCheck = response.getSamplerData(); // TODO - is this where the URL is stored?
-            if (toCheck == null) {
-                toCheck = "";
+            toCheck = "";                
+            final URL url = response.getURL();
+            if (url != null){
+                toCheck = url.toString();                
             }
         }
 
-        if (toCheck.length() == 0) {
-            return result.setResultForNull();
-        }
-
         result.setFailure(false);
         result.setError(false);
 
+        if (toCheck.length() == 0) {
+            if (notTest) {
+                return result;
+            }
+            return result.setResultForNull();
+        }
+
         boolean contains = isContainsType(); // do it once outside loop
         boolean equals = isEqualsType();
         boolean substring = isSubstringType();
         boolean matches = isMatchType();
         boolean debugEnabled = log.isDebugEnabled();
         if (debugEnabled){
-            log.debug("Type:" + (contains?"Contains":"Match") + (not? "(not)": ""));
+            log.debug("Type:" + (contains?"Contains":"Match") + (notTest? "(not)": ""));
         }
         
         try {
@@ -338,7 +343,7 @@ public class ResponseAssertion extends AbstractTestElement implements Serializab
                 } else {
                     found = localMatcher.matches(toCheck, pattern);
                 }
-                pass = not ? !found : found;
+                pass = notTest ? !found : found;
                 if (!pass) {
                     if (debugEnabled){log.debug("Failed: "+stringPattern);}
                     result.setFailure(true);
diff --git a/test/src/org/apache/jmeter/assertions/PackageTest.java b/test/src/org/apache/jmeter/assertions/PackageTest.java
index 5188e5fd3e..908d19f724 100644
--- a/test/src/org/apache/jmeter/assertions/PackageTest.java
+++ b/test/src/org/apache/jmeter/assertions/PackageTest.java
@@ -18,6 +18,9 @@
 
 package org.apache.jmeter.assertions;
 
+import java.net.MalformedURLException;
+import java.net.URL;
+
 import junit.framework.TestCase;
 
 import org.apache.jmeter.junit.JMeterTestCase;
@@ -41,9 +44,9 @@ public class PackageTest extends TestCase {
 		assertEquals("D41D8CD98F00B204E9800998ECF8427E", MD5HexAssertion.baMD5Hex(new byte[] {}).toUpperCase(java.util.Locale.ENGLISH));
 	}
 
-	int threadsRunning;
+	volatile int threadsRunning;
 
-	int failed;
+	volatile int failed;
 
 	public void testThreadSafety() throws Exception {
 		Thread[] threads = new Thread[100];
@@ -259,7 +262,7 @@ public class PackageTest extends TestCase {
 		private JMeterVariables vars;
 		private AssertionResult result;
 		
-		public void setUp() {
+		public void setUp() throws MalformedURLException {
 			jmctx = JMeterContextService.getContext();
 			assertion = new ResponseAssertion();
 			assertion.setThreadContext(jmctx);
@@ -272,7 +275,7 @@ public class PackageTest extends TestCase {
 					"response Data\n" +
 					"line 2\n\nEOF"
 					).getBytes());
-			sample.setSamplerData("Sampler Label");// This is where RA checks the URL!
+			sample.setURL(new URL("http://localhost/Sampler/Data/"));
 			sample.setResponseCode("401");
 			sample.setResponseHeaders("X-Header: abcd");
 		}
diff --git a/xdocs/changes.xml b/xdocs/changes.xml
index 67b08e91dd..4fa7579255 100644
--- a/xdocs/changes.xml
+++ b/xdocs/changes.xml
@@ -110,6 +110,7 @@ Moved the Scoping Rules sub-section from Section 3. "Building a Test Plan"  to S
 <li>Bug 45831 - WS Sampler reports incorrect throughput if SOAP packet creation fails</li>
 <li>Bug 45887 - TCPSampler: timeout property incorrectly set</li>
 <li>Bug 45928 - AJP/1.3 Sampler doesn't retrieve his label from messages.properties</li>
+<li>Bug 45904 - Allow 'Not' Response Assertion to succeed with null sample</li>
 </ul>
 
 <h3>Improvements</h3>