diff --git a/js/src/builtin/RegExp.cpp b/js/src/builtin/RegExp.cpp
index 9c329eac77e5..bb765a2b6769 100644
--- a/js/src/builtin/RegExp.cpp
+++ b/js/src/builtin/RegExp.cpp
@@ -479,26 +479,6 @@ regexp_sticky(JSContext *cx, unsigned argc, JS::Value *vp)
     return CallNonGenericMethod<IsRegExp, regexp_sticky_impl>(cx, args);
 }
 
-/* ES6 draft rev32 21.2.5.15. */
-MOZ_ALWAYS_INLINE bool
-regexp_unicode_impl(JSContext *cx, CallArgs args)
-{
-    MOZ_ASSERT(IsRegExp(args.thisv()));
-
-    /* Steps 4-6. */
-    /* FIXME: When the /u flags is supported, return correct value. */
-    args.rval().setBoolean(false);
-    return true;
-}
-
-static bool
-regexp_unicode(JSContext *cx, unsigned argc, JS::Value *vp)
-{
-    /* Steps 1-3. */
-    CallArgs args = CallArgsFromVp(argc, vp);
-    return CallNonGenericMethod<IsRegExp, regexp_unicode_impl>(cx, args);
-}
-
 static const JSPropertySpec regexp_properties[] = {
     JS_PSG("flags", regexp_flags, 0),
     JS_PSG("global", regexp_global, 0),
@@ -506,7 +486,6 @@ static const JSPropertySpec regexp_properties[] = {
     JS_PSG("multiline", regexp_multiline, 0),
     JS_PSG("source", regexp_source, 0),
     JS_PSG("sticky", regexp_sticky, 0),
-    JS_PSG("unicode", regexp_unicode, 0),
     JS_PS_END
 };
 
diff --git a/js/src/tests/ecma_6/RegExp/descriptor.js b/js/src/tests/ecma_6/RegExp/descriptor.js
index cc545b3a6ae2..62dda8521fb4 100644
--- a/js/src/tests/ecma_6/RegExp/descriptor.js
+++ b/js/src/tests/ecma_6/RegExp/descriptor.js
@@ -10,7 +10,7 @@ var getters = [
   "multiline",
   "source",
   "sticky",
-  "unicode",
+  //"unicode",
 ];
 
 for (var name of getters) {
@@ -21,5 +21,9 @@ for (var name of getters) {
   assertEq("get" in desc, true);
 }
 
+// When the /u flag is supported, remove this comment and the next line, and
+// uncomment "unicode" in |props| above.
+assertThrowsInstanceOf(() => RegExp("", "mygui").flags, SyntaxError);
+
 if (typeof reportCompare === "function")
     reportCompare(true, true);
diff --git a/js/src/tests/ecma_6/RegExp/flag-accessors.js b/js/src/tests/ecma_6/RegExp/flag-accessors.js
index 57ea43cec6a5..4f169c8a4b2c 100644
--- a/js/src/tests/ecma_6/RegExp/flag-accessors.js
+++ b/js/src/tests/ecma_6/RegExp/flag-accessors.js
@@ -8,15 +8,15 @@ var props = [
   "ignoreCase",
   "multiline",
   "sticky",
-  "unicode",
+  //"unicode",
 ];
 
 testThrows(RegExp.prototype);
 test(/foo/iymg, [true, true, true, true, false]);
 test(RegExp(""), [false, false, false, false, false]);
 test(RegExp("", "mygi"), [true, true, true, true, false]);
-// When the /u flag is supported, remove the following line and uncomment the
-// next line.
+// When the /u flag is supported, remove the following line, uncomment the
+// next line, and uncomment "unicode" in |props| above.
 assertThrowsInstanceOf(() => RegExp("", "mygui").flags, SyntaxError);
 // test(RegExp("", "mygiu"), [true, true, true, true, true]);