diff --git a/Makefile b/Makefile
index 425c519ede..01b6643bdf 100644
--- a/Makefile
+++ b/Makefile
@@ -243,6 +243,10 @@ ifeq ($(uname_S),NetBSD)
 	ALL_CFLAGS += -I/usr/pkg/include
 	ALL_LDFLAGS += -L/usr/pkg/lib -Wl,-rpath,/usr/pkg/lib
 endif
+ifeq ($(uname_S),AIX)
+	NO_STRCASESTR=YesPlease
+	NEEDS_LIBICONV=YesPlease
+endif
 ifneq (,$(findstring arm,$(uname_M)))
 	ARM_SHA1 = YesPlease
 endif
diff --git a/convert-objects.c b/convert-objects.c
index d78a8b4ae3..b49bce2681 100644
--- a/convert-objects.c
+++ b/convert-objects.c
@@ -1,4 +1,5 @@
-#define _XOPEN_SOURCE /* glibc2 needs this */
+#define _XOPEN_SOURCE 500 /* glibc2 and AIX 5.3L need this */
+#define _XOPEN_SOURCE_EXTENDED 1 /* AIX 5.3L needs this */
 #include <time.h>
 #include "cache.h"
 
diff --git a/mailinfo.c b/mailinfo.c
index 3b97a893f0..d4b4163628 100644
--- a/mailinfo.c
+++ b/mailinfo.c
@@ -8,6 +8,7 @@
 #include <string.h>
 #include <ctype.h>
 #include <iconv.h>
+#include "git-compat-util.h"
 #include "cache.h"
 
 static FILE *cmitmsg, *patchfile;