diff --git a/org.eclipse.jgit.http.test/tst/org/eclipse/jgit/http/test/SmartClientSmartServerTest.java b/org.eclipse.jgit.http.test/tst/org/eclipse/jgit/http/test/SmartClientSmartServerTest.java
index 82861ed9b..0f3d3c6cf 100644
--- a/org.eclipse.jgit.http.test/tst/org/eclipse/jgit/http/test/SmartClientSmartServerTest.java
+++ b/org.eclipse.jgit.http.test/tst/org/eclipse/jgit/http/test/SmartClientSmartServerTest.java
@@ -56,6 +56,7 @@
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.net.URISyntaxException;
+import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
@@ -89,6 +90,8 @@
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.NullProgressMonitor;
 import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectIdRef;
+import org.eclipse.jgit.lib.ObjectInserter;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.ReflogEntry;
 import org.eclipse.jgit.lib.ReflogReader;
@@ -486,6 +489,25 @@ public void testInitialClone_BrokenServer() throws Exception {
 				service.getResponseHeader(HDR_CONTENT_TYPE));
 	}
 
+	@Test
+	public void testInvalidWant() throws Exception {
+		@SuppressWarnings("resource")
+		ObjectId id = new ObjectInserter.Formatter().idFor(Constants.OBJ_BLOB,
+				"testInvalidWant".getBytes(StandardCharsets.UTF_8));
+
+		Repository dst = createBareRepository();
+		try (Transport t = Transport.open(dst, remoteURI);
+				FetchConnection c = t.openFetch()) {
+			Ref want = new ObjectIdRef.Unpeeled(Ref.Storage.NETWORK, id.name(),
+					id);
+			c.fetch(NullProgressMonitor.INSTANCE, Collections.singleton(want),
+					Collections.<ObjectId> emptySet());
+			fail("Server accepted want " + id.name());
+		} catch (TransportException err) {
+			assertEquals("want " + id.name() + " not valid", err.getMessage());
+		}
+	}
+
 	@Test
 	public void testPush_NotAuthorized() throws Exception {
 		final TestRepository src = createTestRepository();
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/UploadPack.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/UploadPack.java
index 101057fb4..8c1f99d22 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/UploadPack.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/UploadPack.java
@@ -742,10 +742,6 @@ else if (requestValidator instanceof AnyRequestValidator)
 			if (!clientShallowCommits.isEmpty())
 				walk.assumeShallow(clientShallowCommits);
 			sendPack = negotiate();
-		} catch (PackProtocolException err) {
-			reportErrorDuringNegotiate(err.getMessage());
-			throw err;
-
 		} catch (ServiceMayNotContinueException err) {
 			if (!err.isOutput() && err.getMessage() != null) {
 				try {
@@ -756,15 +752,20 @@ else if (requestValidator instanceof AnyRequestValidator)
 				}
 			}
 			throw err;
-
-		} catch (IOException err) {
-			reportErrorDuringNegotiate(JGitText.get().internalServerError);
-			throw err;
-		} catch (RuntimeException err) {
-			reportErrorDuringNegotiate(JGitText.get().internalServerError);
-			throw err;
-		} catch (Error err) {
-			reportErrorDuringNegotiate(JGitText.get().internalServerError);
+		} catch (IOException | RuntimeException | Error err) {
+			boolean output = false;
+			try {
+				String msg = err instanceof PackProtocolException
+						? err.getMessage()
+						: JGitText.get().internalServerError;
+				pckOut.writeString("ERR " + msg + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
+				output = true;
+			} catch (Throwable err2) {
+				// Ignore this secondary failure, leave output false.
+			}
+			if (output) {
+				throw new UploadPackInternalServerErrorException(err);
+			}
 			throw err;
 		}
 
@@ -781,14 +782,6 @@ private static Set<ObjectId> refIdSet(Collection<Ref> refs) {
 		return ids;
 	}
 
-	private void reportErrorDuringNegotiate(String msg) {
-		try {
-			pckOut.writeString("ERR " + msg + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
-		} catch (Throwable err) {
-			// Ignore this secondary failure.
-		}
-	}
-
 	private void processShallow() throws IOException {
 		try (DepthWalk.RevWalk depthWalk = new DepthWalk.RevWalk(
 				walk.getObjectReader(), depth)) {