diff --git a/paramiko/py3compat.py b/paramiko/py3compat.py
index 2228599..8842b98 100644
--- a/paramiko/py3compat.py
+++ b/paramiko/py3compat.py
@@ -113,7 +113,9 @@ else:
         return s
 
     def byte_ord(c):
-        assert isinstance(c, int)
+        # In case we're handed a string instead of an int.
+        if not isinstance(c, int):
+            c = ord(c)
         return c
 
     def byte_chr(c):