diff --git a/vendor/plugins/rfpdf/lib/tcpdf.rb b/vendor/plugins/rfpdf/lib/tcpdf.rb
index da7d556f..1e444305 100755
--- a/vendor/plugins/rfpdf/lib/tcpdf.rb
+++ b/vendor/plugins/rfpdf/lib/tcpdf.rb
@@ -3063,7 +3063,7 @@ class TCPDF
 			out('/Filter /FlateDecode');
 		end
 		out('>>');
-    open(ctgfile) do |f|
+    open(ctgfile, "rb") do |f|
       putstream(f.read())
     end
 		out('endobj');