diff --git a/lib/compress.js b/lib/compress.js
index f7407523..7d1f8cc3 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -4655,6 +4655,7 @@ merge(Compressor.prototype, {
         var arg_index;
         if (consequent instanceof AST_Call
             && alternative.TYPE === consequent.TYPE
+            && consequent.args.length == alternative.args.length
             && consequent.expression.equivalent_to(alternative.expression)
             && !self.condition.has_side_effects(compressor)
             && !consequent.expression.has_side_effects(compressor)
@@ -4766,9 +4767,7 @@ merge(Compressor.prototype, {
         function single_arg_diff() {
             var a = consequent.args;
             var b = alternative.args;
-            var len = a.length;
-            if (len != b.length) return;
-            for (var i = 0; i < len; i++) {
+            for (var i = 0, len = a.length; i < len; i++) {
                 if (!a[i].equivalent_to(b[i])) {
                     for (var j = i + 1; j < len; j++) {
                         if (!a[j].equivalent_to(b[j])) return;