diff --git a/lib/builder.rb b/lib/builder.rb
index 4340e89c..ad4ef53a 100644
--- a/lib/builder.rb
+++ b/lib/builder.rb
@@ -49,7 +49,7 @@ class CustomWizard::Builder
       result
     end
 
-    result.gsub!(/w\{(.*?)\}/) { |match| data[$1.to_sym] }
+    result.gsub(/w\{(.*?)\}/) { |match| data[$1.to_sym] }
   end
 
   def build(build_opts = {})