1 files changed, 9 insertions, 1 deletions
diff --git a/numpy/compat/py3k.py b/numpy/compat/py3k.py
index 3d10bb988..d02c9f8fe 100644
--- a/numpy/compat/py3k.py
+++ b/numpy/compat/py3k.py
@@ -47,7 +47,15 @@ def asstr(s):
     return str(s)
 
 def isfileobj(f):
-    return isinstance(f, (io.FileIO, io.BufferedReader, io.BufferedWriter))
+    if not isinstance(f, (io.FileIO, io.BufferedReader, io.BufferedWriter)):
+        return False
+    try:
+        # BufferedReader/Writer may raise OSError when
+        # fetching `fileno()` (e.g. when wrapping BytesIO).
+        f.fileno()
+        return True
+    except OSError:
+        return False
 
 def open_latin1(filename, mode='r'):
     return open(filename, mode=mode, encoding='iso-8859-1')