--- a/layout/style/test/test_font_loading_api.html
+++ b/layout/style/test/test_font_loading_api.html
@@ -302,16 +302,19 @@ function runTest() {
           is(aError.name, "SyntaxError", "FontFace.loaded with invalid family name " + aFamilyName + " should be rejected with a SyntaxError (TEST 17)");
         });
       });
     });
     return familyTests;
 
   }).then(function() {
 
+    // XXX Disabled this sub-test due to intermittent failures (bug 1076803).
+    return;
+
     // (TEST 18) Test passing valid url() source strings to the FontFace
     // constructor.
     var srcTests = Promise.resolve();
     gCSSFontFaceDescriptors.src.values.forEach(function(aSrc) {
       srcTests = srcTests.then(function() {
         var face = new FontFace("test", aSrc);
         return face.load().then(function() {
           ok(true, "FontFace should load with valid url() src " + aSrc + " (TEST 18)");