diff --git a/spacy/cfile.pyx b/spacy/cfile.pyx
index cb192dfab..89e22d413 100644
--- a/spacy/cfile.pyx
+++ b/spacy/cfile.pyx
@@ -2,7 +2,9 @@ from libc.stdio cimport fopen, fclose, fread, fwrite, FILE
 
 
 cdef class CFile:
-    def __init__(self, loc, bytes mode):
+    def __init__(self, loc, mode):
+        if isinstance(mode, unicode):
+            mode_str = mode.decode('ascii')
         cdef bytes bytes_loc = loc.encode('utf8') if type(loc) == unicode else loc
         self.fp = fopen(<char*>bytes_loc, mode)
         if self.fp == NULL: