diff --git a/src/uw_tmp.h1 b/src/uw_tmp.h1
index 57231fb..2d5e994 100644
--- a/src/uw_tmp.h1
+++ b/src/uw_tmp.h1
@@ -3,7 +3,17 @@
 
 /* sysdep: -utmpx */
 
+#ifdef _PATH_UTMP
 #define UW_TMP_UFILE _PATH_UTMP
 #define UW_TMP_WFILE _PATH_WTMP
+#else
+/* AIX only has UTMP_FILE */
+#ifdef UTMP_FILE
+#define UW_TMP_UFILE UTMP_FILE
+#define UW_TMP_WFILE WTMP_FILE
+#else
+#error neither _PATH_UTMP nor UTMP_FILE defined.
+#endif
+#endif
 
 typedef struct utmp uw_tmp;