diff --git a/lib/compress.js b/lib/compress.js
index fd3f7a21..1e99f158 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -1745,6 +1745,7 @@ merge(Compressor.prototype, {
                             } catch(ex) {
                                 if (ex !== ast) throw ex;
                             };
+                            if (!fun) return self;
                             var args = fun.argnames.map(function(arg, i){
                                 return make_node(AST_String, self.args[i], {
                                     value: arg.print_to_string()