diff --git a/python/obitools3/uri/decode.pyx b/python/obitools3/uri/decode.pyx
index db844e1..2c8a95b 100644
--- a/python/obitools3/uri/decode.pyx
+++ b/python/obitools3/uri/decode.pyx
@@ -174,7 +174,7 @@ def open_uri(uri,
              dms_only=False,
              force_file=False):
 
-    if not uri.isascii():
+    if type(uri) == str and not uri.isascii():
         raise Exception("Paths must be ASCII characters only")
             
     cdef bytes urib = tobytes(uri)