diff --git a/CHANGES b/CHANGES
index e48e9b5919aa6e4c9403c22d4f5aa78025c40e27..f99ce348a906f086d0a8c35b3b5c53d8523c09da 100644
--- a/CHANGES
+++ b/CHANGES
@@ -6,6 +6,11 @@
 
                                   Changelog
 
+Daniel S (31 July 2007)
+- Peter O'Gorman pointed out (and fixed) that the non-blocking check in
+  configure made libcurl use blocking sockets on AIX 4 and 5, while that
+  wasn't the intention.
+
 Daniel S (29 July 2007)
 - Jayesh A Shah filed bug report #1759542
   (http://curl.haxx.se/bug/view.cgi?id=1759542) identifying a rather serious
diff --git a/acinclude.m4 b/acinclude.m4
index bf0c4b42dd06123ad49ba3bb9932996091005b4a..53c8b1e3bb1cbc2abc761adf6f53f83e5e364722 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -1107,7 +1107,7 @@ AC_DEFUN([CURL_CHECK_NONBLOCKING_SOCKET],
 #  define PLATFORM_SUNOS4
 # endif
 #endif
-#if (defined(_AIX) || defined(__xlC__)) && !defined(_AIX4)
+#if (defined(_AIX) || defined(__xlC__)) && !defined(_AIX41)
 # define PLATFORM_AIX_V3
 #endif