Fixes #299

src/main/java/org/littleshoot/proxy/impl/ClientToProxyConnection.java

@@ -46,7 +46,6 @@
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
-import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.atomic.AtomicBoolean;
@@ -1243,12 +1242,7 @@ private void stripConnectionTokens(HttpHeaders headers) {
      *            The headers to modify
      */
     private void stripHopByHopHeaders(HttpHeaders headers) {
-        Set<String> headerNames = headers.names();
-        for (String headerName : headerNames) {
-            if (ProxyUtils.shouldRemoveHopByHopHeader(headerName)) {
-                headers.remove(headerName);
-            }
-        }
+    	ProxyUtils.stripHopByHopHeaders(headers);
     }
 
     /* *************************************************************************

src/main/java/org/littleshoot/proxy/impl/ProxyUtils.java

@@ -519,6 +519,18 @@ public static boolean shouldRemoveHopByHopHeader(String headerName) {
         return SHOULD_NOT_PROXY_HOP_BY_HOP_HEADERS.contains(headerName);
     }
 
+    /**
+     * Removes all headers that should not be forwarded. See RFC 2616 13.5.1
+     * End-to-end and Hop-by-hop Headers.
+     *
+     * @param headers
+     *            The headers to modify
+     */
+    public static void stripHopByHopHeaders(HttpHeaders headers) {
+      // Not explicitly documented, but remove is case insensitve as a HTTP header handling function should be
+      SHOULD_NOT_PROXY_HOP_BY_HOP_HEADERS.forEach(headers::remove);
+    }    
+
     /**
      * Splits comma-separated header values into tokens. For example, if the value of the Connection header is "Transfer-Encoding, close",
      * this method will return "Transfer-Encoding" and "close". This method strips trims any optional whitespace from

src/test/java/org/littleshoot/proxy/ProxyHeadersTest.java

@@ -12,11 +12,14 @@
 import org.mockserver.integration.ClientAndServer;
 import org.mockserver.matchers.Times;
 import org.mockserver.model.ConnectionOptions;
+import org.mockserver.model.HttpRequest;
+import org.mockserver.model.NottableString;
 
 import static org.hamcrest.Matchers.emptyArray;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.mockserver.model.HttpRequest.request;
 import static org.mockserver.model.HttpResponse.response;
+import static org.junit.Assert.assertEquals;
 
 /**
  * Tests the proxy's handling and manipulation of headers.
@@ -74,4 +77,27 @@ public void testProxyRemovesConnectionHeadersFromServer() throws Exception {
             assertThat("Expected proxy to remove the Dummy-Header specified in the Connection header", dummyHeaders, emptyArray());
         }
     }
+
+	@Test
+	public void testProxyRemovesHopByHopHeadersFromClient() throws Exception {
+		HttpRequest expectedServerRequest = request() //
+				.withMethod("GET") //
+				.withPath("/connectionheaders") //
+				.withHeader(NottableString.not("proxy-authenticate")) //
+				.withHeader(NottableString.not("proxy-authorization"));
+		mockServer.when(expectedServerRequest, Times.exactly(1)) //
+				.respond(response().withStatusCode(200).withBody("success"));
+
+		this.proxyServer = DefaultHttpProxyServer.bootstrap().withPort(0).start();
+
+		try (CloseableHttpClient httpClient = TestUtils
+				.createProxiedHttpClient(proxyServer.getListenAddress().getPort())) {
+			HttpGet clientRequest = new HttpGet("http://localhost:" + mockServerPort + "/connectionheaders");
+			clientRequest.addHeader("Proxy-Authenticate", "");
+			clientRequest.addHeader("Proxy-Authorization", "");
+			HttpResponse response = httpClient.execute(clientRequest);
+			EntityUtils.consume(response.getEntity());
+			assertEquals(200, response.getStatusLine().getStatusCode());
+		}
+	}
 }