diff --git a/lib/paperclip/attachment.rb b/lib/paperclip/attachment.rb
index b321c8c52..3d4ea4df7 100644
--- a/lib/paperclip/attachment.rb
+++ b/lib/paperclip/attachment.rb
@@ -77,7 +77,7 @@ def assign uploaded_file
       return nil if uploaded_file.nil?
 
       @queued_for_write[:original]   = uploaded_file.to_tempfile
-      instance_write(:file_name,       uploaded_file.original_filename.strip.gsub(/[^\w\d\.\-]+/, '_'))
+      instance_write(:file_name,       uploaded_file.original_filename.strip.gsub(/[^A-Za-z\d\.\-_]+/, '_'))
       instance_write(:content_type,    uploaded_file.content_type.to_s.strip)
       instance_write(:file_size,       uploaded_file.size.to_i)
       instance_write(:updated_at,      Time.now)