diff --git a/src/s/aix4.h b/src/s/aix4.h
index ae55ae3b317..9f04d5aa25c 100644
--- a/src/s/aix4.h
+++ b/src/s/aix4.h
@@ -4,3 +4,12 @@
 
 /* AIX 4 does not have HFT any more.  */
 #undef AIXHFT
+
+/* string.h defines rindex as a macro, at least with native cc, so we
+   lose declaring char * rindex without this.
+   It is just a guess which versions of AIX need this definition.  */
+#undef HAVE_STRING_H
+
+/* Dave Love <d.love@dl.ac.uk> reported this as needed on AIX 4.1.
+   It is just a guess which versions of AIX need this definition.  */
+#define HAVE_WAIT_HEADER