diff --git a/Misc/NEWS b/Misc/NEWS
index 6948fc6fc26..4e49d8f7407 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -72,6 +72,9 @@ C-API
 Library
 -------
 
+- Issue #6236, #6348: Fix various failures in the I/O library under AIX
+  and other platforms, when using a non-gcc compiler. Patch by egreen.
+
 - Issue #4606: Passing 'None' if ctypes argtype is set to POINTER(...)
   does now always result in NULL.
 
diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c
index 4e7c721adda..438848bc908 100644
--- a/Modules/_io/fileio.c
+++ b/Modules/_io/fileio.c
@@ -45,10 +45,10 @@
 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 */
+	unsigned int closefd : 1;
 	PyObject *weakreflist;
 	PyObject *dict;
 } fileio;
diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
index b91852e3516..333c93f9208 100644
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -190,9 +190,9 @@ typedef struct {
     PyObject_HEAD
     PyObject *decoder;
     PyObject *errors;
-    int pendingcr:1;
-    int translate:1;
-    unsigned int seennl:3;
+    signed int pendingcr: 1;
+    signed int translate: 1;
+    unsigned int seennl: 3;
 } nldecoder_object;
 
 static int