gistfile1.txt

kronos:rubinius kronos$ git diff
diff --git a/lib/strscan.rb b/lib/strscan.rb
index 1d70184..4e3d9f4 100644
--- a/lib/strscan.rb
+++ b/lib/strscan.rb
@@ -124,7 +124,7 @@ class StringScanner
   end
 
   def pre_match
-    string[0...(pos - match.to_s.size)] if matched?
+    string[0...(@prev_pos + match.begin(0))] if matched?
   end
 
   def reset_state