diff --git a/mozilla/js/ref/jsinterp.c b/mozilla/js/ref/jsinterp.c
index 6262aef03bf..0bc14265b9d 100644
--- a/mozilla/js/ref/jsinterp.c
+++ b/mozilla/js/ref/jsinterp.c
@@ -2242,7 +2242,8 @@ js_Interpret(JSContext *cx, jsval *result)
 	    /*
 	     * ECMAv2 forbids conversion of discriminant, so we will skip to
 	     * the default case if the discriminant isn't an int jsval.
-	     * (This opcode is only emitted for all-integer switches.)
+	     * (This opcode is emitted only for dense jsint-domain switches.)
+	     * XXX don't use JSVERSION_IS_ECMAv2, it's wrong and overloaded
 	     */
 	    if (cx->version == JSVERSION_DEFAULT ||
 		cx->version >= JSVERSION_1_4) {