diff --git a/Lib/fileinput.py b/Lib/fileinput.py
index 19932ca..ba48575 100644
--- a/Lib/fileinput.py
+++ b/Lib/fileinput.py
@@ -226,7 +226,7 @@
         self._mode = mode
         if inplace and openhook:
             raise ValueError("FileInput cannot use an opening hook in inplace mode")
-        elif openhook and not callable(openhook):
+        elif openhook and not hasattr(openhook, '__call__'):
             raise ValueError("FileInput openhook must be callable")
         self._openhook = openhook