rindex is defined in strings.h
diff --git a/ltrace-elf.c b/ltrace-elf.c
index c571d2a..f4f4375 100644
--- a/ltrace-elf.c
+++ b/ltrace-elf.c
@@ -40,6 +40,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <unistd.h>
 
 #include "backend.h"