diff --git a/Misc/NEWS b/Misc/NEWS
index 900acc861aa..b4b9851b9cd 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -82,6 +82,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #6236, #6348: Fix various failures in the `io` module under AIX
+  and other platforms, when using a non-gcc compiler. Patch by egreen.
+
 - Issue #6851: Fix urllib.urlopen crash on secondairy threads on OSX 10.6
 
 - Issue #6947: Fix distutils test on windows. Patch by Hirokazu Yamamoto.
diff --git a/Modules/_fileio.c b/Modules/_fileio.c
index fbe4189a8da..5a3613ba375 100644
--- a/Modules/_fileio.c
+++ b/Modules/_fileio.c
@@ -30,10 +30,10 @@
 typedef struct {
 	PyObject_HEAD
 	int fd;
-	unsigned readable : 1;
-	unsigned writable : 1;
-	int seekable : 2; /* -1 means unknown */
-	int closefd : 1;
+	unsigned int readable : 1;
+	unsigned int writable : 1;
+	signed int seekable : 2; /* -1 means unknown */
+	signed int closefd : 1;
 	PyObject *weakreflist;
 } PyFileIOObject;