diff --git a/rubberin b/rubberin
index 3debd1d..1d5ef2d 100755
--- a/rubberin
+++ b/rubberin
@@ -79,11 +79,11 @@ def view(infile, mode)
   case mode
     when :dvi
       exec "xdvi.bin", "-watchfile", "1", 
-                       "-name", "xdvi",  infile.with_extname('dvi')
+                       "-name", "xdvi",  infile.with_extname('dvi').to_s
     when :ps
-      exec "evince", infile.with_extname('ps')
+      exec "evince", infile.with_extname('ps').to_s
     when :pdf, :pspdf
-      exec "evince", infile.with_extname('pdf')
+      exec "evince", infile.with_extname('pdf').to_s
   end
 end
 
@@ -98,9 +98,9 @@ end
 def reload(infile, mode)
   case mode
     when :ps
-      system "evince", infile.with_extname('ps')
+      system "evince", infile.with_extname('ps').to_s
     when :pdf, :pspdf
-      system "evince", infile.with_extname('pdf')
+      system "evince", infile.with_extname('pdf').to_s
   end
 end