diff --git a/lib/output.js b/lib/output.js
index b9637929..f4ec36b1 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -1153,7 +1153,12 @@ function OutputStream(options) {
     };
 
     DEFPRINT(AST_RegExp, function(self, output){
-        var str = self.getValue().toString();
+        var str = self.getValue()
+        try {
+            str = str.toString();
+        } catch (e) {
+            throw new Error('Cannot evaluate RegExp [' + self.start.file + ':' + self.start.line + ',' + self.start.col + ']');
+        }
         if (output.option("ascii_only")) {
             str = output.to_ascii(str);
         } else if (output.option("unescape_regexps")) {