diff --git a/lib/fastimage.rb b/lib/fastimage.rb
index 8694557..3138759 100644
--- a/lib/fastimage.rb
+++ b/lib/fastimage.rb
@@ -282,8 +282,8 @@ def escaped_location(location)
     begin
       URI(location)
     rescue URI::InvalidURIError
-      if defined?(ERB::Util)
-        ERB::Util.url_encode(location)
+      if defined?(::ERB::Util)
+        ::ERB::Util.url_encode(location)
       else
         URI.escape(location)
       end