diff --git a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/DeleteDraftPatchSetIT.java b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/DeleteDraftPatchSetIT.java
index 10fbed0..2442b595 100644
--- a/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/DeleteDraftPatchSetIT.java
+++ b/gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/change/DeleteDraftPatchSetIT.java
@@ -57,7 +57,7 @@
     assertEquals(triplet, c.id);
     assertEquals(ChangeStatus.DRAFT, c.status);
     RestResponse r = deletePatchSet(changeId, ps, userSession);
-    assertEquals("Not found", r.getEntityContent());
+    assertEquals("Not found: " + changeId, r.getEntityContent());
     assertEquals(404, r.getStatusCode());
   }
 
diff --git a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/ResourceNotFoundException.java b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/ResourceNotFoundException.java
index 76942e6..611812a 100644
--- a/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/ResourceNotFoundException.java
+++ b/gerrit-extension-api/src/main/java/com/google/gerrit/extensions/restapi/ResourceNotFoundException.java
@@ -22,19 +22,17 @@
   public ResourceNotFoundException() {
   }
 
-  /** @param id portion of the resource URI that does not exist. */
-  public ResourceNotFoundException(String id) {
-    super(id);
+  public ResourceNotFoundException(String msg) {
+    super(msg);
   }
 
-  /** @param id portion of the resource URI that does not exist. */
-  public ResourceNotFoundException(String id, Throwable cause) {
-    super(id, cause);
+  public ResourceNotFoundException(String msg, Throwable cause) {
+    super(msg, cause);
   }
 
   /** @param id portion of the resource URI that does not exist. */
   public ResourceNotFoundException(IdString id) {
-    super(id.get());
+    super("Not found: " + id.get());
   }
 
   @SuppressWarnings("unchecked")
diff --git a/gerrit-httpd/src/main/java/com/google/gerrit/httpd/restapi/RestApiServlet.java b/gerrit-httpd/src/main/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
index bf29c60..634e3e9 100644
--- a/gerrit-httpd/src/main/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
+++ b/gerrit-httpd/src/main/java/com/google/gerrit/httpd/restapi/RestApiServlet.java
@@ -32,7 +32,6 @@
 
 import com.google.common.base.Function;
 import com.google.common.base.Joiner;
-import com.google.common.base.MoreObjects;
 import com.google.common.base.Splitter;
 import com.google.common.base.Strings;
 import com.google.common.collect.ImmutableMultimap;
@@ -345,27 +344,34 @@
         }
       }
     } catch (AuthException e) {
-      replyError(req, res, status = SC_FORBIDDEN, e.getMessage(), e.caching(), e);
+      replyError(req, res, status = SC_FORBIDDEN, messageOr(e, "Forbidden"),
+          e.caching(), e);
     } catch (BadRequestException e) {
-      replyError(req, res, status = SC_BAD_REQUEST, e.getMessage(), e.caching(), e);
+      replyError(req, res, status = SC_BAD_REQUEST, messageOr(e, "Bad request"),
+          e.caching(), e);
     } catch (MethodNotAllowedException e) {
-      replyError(req, res, status = SC_METHOD_NOT_ALLOWED, "Method not allowed", e.caching(), e);
+      replyError(req, res, status = SC_METHOD_NOT_ALLOWED,
+          messageOr(e, "Method not allowed"), e.caching(), e);
     } catch (ResourceConflictException e) {
-      replyError(req, res, status = SC_CONFLICT, e.getMessage(), e.caching(), e);
+      replyError(req, res, status = SC_CONFLICT, messageOr(e, "Conflict"),
+          e.caching(), e);
     } catch (PreconditionFailedException e) {
       replyError(req, res, status = SC_PRECONDITION_FAILED,
-          MoreObjects.firstNonNull(e.getMessage(), "Precondition failed"), e.caching(), e);
+          messageOr(e, "Precondition failed"), e.caching(), e);
     } catch (ResourceNotFoundException e) {
-      replyError(req, res, status = SC_NOT_FOUND, "Not found", e.caching(), e);
+      replyError(req, res, status = SC_NOT_FOUND, messageOr(e, "Not found"),
+          e.caching(), e);
     } catch (UnprocessableEntityException e) {
-      replyError(req, res, status = 422,
-          MoreObjects.firstNonNull(e.getMessage(), "Unprocessable Entity"), e.caching(), e);
+      replyError(req, res, status = 422, messageOr(e, "Unprocessable Entity"),
+          e.caching(), e);
     } catch (AmbiguousViewException e) {
-      replyError(req, res, status = SC_NOT_FOUND, e.getMessage(), e);
+      replyError(req, res, status = SC_NOT_FOUND, messageOr(e, "Ambiguous"), e);
     } catch (MalformedJsonException e) {
-      replyError(req, res, status = SC_BAD_REQUEST, "Invalid " + JSON_TYPE + " in request", e);
+      replyError(req, res, status = SC_BAD_REQUEST,
+          "Invalid " + JSON_TYPE + " in request", e);
     } catch (JsonParseException e) {
-      replyError(req, res, status = SC_BAD_REQUEST, "Invalid " + JSON_TYPE + " in request", e);
+      replyError(req, res, status = SC_BAD_REQUEST,
+          "Invalid " + JSON_TYPE + " in request", e);
     } catch (Exception e) {
       status = SC_INTERNAL_SERVER_ERROR;
       handleException(e, req, res);
@@ -377,6 +383,13 @@
     }
   }
 
+  private static String messageOr(Throwable t, String defaultMessage) {
+    if (!Strings.isNullOrEmpty(t.getMessage())) {
+      return t.getMessage();
+    }
+    return defaultMessage;
+  }
+
   private static boolean notModified(HttpServletRequest req, RestResource rsrc) {
     if (!isGetOrHead(req)) {
       return false;