diff --git a/lib/freedom_patches/sprockets_patches.rb b/lib/freedom_patches/sprockets_patches.rb
index 78fc2264bd2..0269580d776 100644
--- a/lib/freedom_patches/sprockets_patches.rb
+++ b/lib/freedom_patches/sprockets_patches.rb
@@ -53,6 +53,6 @@ if Rails.env == "development"
     end
   end
 
-  Sprockets.register_bundle_metadata_reducer 'application/javascript', :data, proc { "" }, ::SprocketHack.method(:concat_javascript_sources)
+  Sprockets.register_bundle_metadata_reducer 'application/javascript', :data, proc { +"" }, ::SprocketHack.method(:concat_javascript_sources)
 
 end
diff --git a/lib/source_url.rb b/lib/source_url.rb
index a7d2ea465a7..8613dcc6b39 100644
--- a/lib/source_url.rb
+++ b/lib/source_url.rb
@@ -16,7 +16,7 @@ class SourceURL < Tilt::Template
   end
 
   def evaluate(scope, locals, &block)
-    code = "eval("
+    code = +"eval("
     code << data.inspect
     code << " + \"\\n//# sourceURL=#{scope.logical_path}\""
     code << ");\n"