diff --git a/lib/compress.js b/lib/compress.js
index efdb49fe..ec571b3a 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1715,7 +1715,7 @@ merge(Compressor.prototype, {
 
     OPT(AST_Binary, function(self, compressor){
         function reverse(op) {
-            if (!(self.left.has_side_effects() && self.right.has_side_effects())) {
+            if (!(self.left.has_side_effects() || self.right.has_side_effects())) {
                 if (op) self.operator = op;
                 var tmp = self.left;
                 self.left = self.right;