diff --git a/test/src/net/sourceforge/plantuml/servlet/TestImage.java b/test/src/net/sourceforge/plantuml/servlet/TestImage.java
index 746df00..ab4e936 100644
--- a/test/src/net/sourceforge/plantuml/servlet/TestImage.java
+++ b/test/src/net/sourceforge/plantuml/servlet/TestImage.java
@@ -5,6 +5,9 @@ import com.meterware.httpunit.*;
 
 import java.io.ByteArrayOutputStream;
 import java.io.InputStream;
+import java.util.Date;
+import java.util.Locale;
+import java.text.SimpleDateFormat;
 
 public class TestImage extends TestCase {
     /**
@@ -16,7 +19,7 @@ public class TestImage extends TestCase {
         WebResponse response = conversation.getResource( request);
         // Analyze response
         // Verifies the Content-Type header
-        assertEquals( "image/png", response.getContentType());
+        assertEquals( "Response content type is not PNG", "image/png", response.getContentType());
         // Get the image and verify its size 
         InputStream responseStream = response.getInputStream();
         ByteArrayOutputStream imageStream = new ByteArrayOutputStream();
@@ -32,4 +35,25 @@ public class TestImage extends TestCase {
         assertTrue( diagramLen > 10000);
         assertTrue( diagramLen < 20000); 
     }
+
+    /**
+     * Verifies that the HTTP header of a diagram incites the browser to cache it.
+     */
+    public void testDiagramHttpHeader() throws Exception {
+        WebConversation conversation = new WebConversation();
+        // Bob -> Alice : hello 
+        WebRequest request = new GetMethodWebRequest( TestUtils.getServerUrl()+"img/SyfFKj2rKt3CoKnELR1Io4ZDoSa70000");
+        WebResponse response = conversation.getResource( request);
+        // Analyze response
+        // Verifies the Content-Type header
+        assertEquals( "Response content type is not PNG", "image/png", response.getContentType());
+        // Verifies the availability of the Expires entry in the response header
+        assertNotNull( response.getHeaderField( "Expires"));
+        // Verifies the availability of the Last-Modified entry in the response header
+        assertNotNull( response.getHeaderField( "Last-Modified"));
+        // Verifies the Last-Modified value is in the past
+        SimpleDateFormat format = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss ZZZ", Locale.ENGLISH);
+        Date lastModified = format.parse( response.getHeaderField( "Last-Modified"));
+        assertTrue( "Last-Modified is not in the past", lastModified.before( new Date()));
+    }
 }