diff -r 45dcdd8f3211 Modules/_io/fileio.c
--- a/Modules/_io/fileio.c	Tue Jul 01 16:48:42 2014 +0200
+++ b/Modules/_io/fileio.c	Tue Jul 01 17:05:50 2014 +0200
@@ -694,9 +694,9 @@ fileio_readall(fileio *self)
                 }
                 continue;
             }
-            if (bytes_read > 0)
-                break;
             if (errno == EAGAIN) {
+                if (bytes_read > 0)
+                    break;
                 Py_DECREF(result);
                 Py_RETURN_NONE;
             }