diff --git a/lib/compress.js b/lib/compress.js
index 121e312a..13ae7c70 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -2067,7 +2067,8 @@ merge(Compressor.prototype, {
                     && self.left.right instanceof AST_Constant
                     && self.right instanceof AST_Binary
                     && self.right.operator == "+"
-                    && self.right.left instanceof AST_Constant) {
+                    && self.right.left instanceof AST_Constant
+                    && self.right.is_string(compressor)) {
                     self = make_node(AST_Binary, self, {
                         operator: "+",
                         left: make_node(AST_Binary, self.left, {
diff --git a/test/compress/issue-126.js b/test/compress/issue-126.js
index 1e654941..7a597b87 100644
--- a/test/compress/issue-126.js
+++ b/test/compress/issue-126.js
@@ -10,6 +10,7 @@ concatenate_rhs_strings: {
         foo(bar() + 123 + "Hello" + "World" + ("Foo" + "Bar"));
         foo("Foo" + "Bar" + bar() + 123 + "Hello" + "World" + ("Foo" + "Bar"));
         foo("Hello" + bar() + 123 + "World");
+        foo(bar() + 'Foo' + (10 + parseInt('10')));
     }
     expect: {
         foo(bar() + 123 + "HelloWorld");
@@ -18,5 +19,6 @@ concatenate_rhs_strings: {
         foo(bar() + 123 + "HelloWorldFooBar");
         foo("FooBar" + bar() + "123HelloWorldFooBar");
         foo("Hello" + bar() + "123World");
+        foo(bar() + 'Foo' + (10 + parseInt('10')));
     }
 }