diff --git a/lib/output.js b/lib/output.js
index defd0215..a13c92ea 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -351,7 +351,9 @@ function OutputStream(options) {
     AST_Node.DEFMETHOD("print", function(stream, force_parens){
         var self = this, generator = self._codegen;
         stream.push_node(self);
-        if (force_parens || self.needs_parens(stream)) {
+        var needs_parens = self.needs_parens(stream);
+        var fc = self instanceof AST_Function && !stream.option("beautify");
+        if (force_parens || (needs_parens && !fc)) {
             stream.with_parens(function(){
                 self.add_comments(stream);
                 self.add_source_map(stream);
@@ -359,6 +361,7 @@ function OutputStream(options) {
             });
         } else {
             self.add_comments(stream);
+            if (needs_parens && fc) stream.print("!");
             self.add_source_map(stream);
             generator(self, stream);
         }