diff --git a/scsh/rx/regexp1.c b/scsh/rx/regexp1.c
index 2be2262..68dea97 100644
--- a/scsh/rx/regexp1.c
+++ b/scsh/rx/regexp1.c
@@ -8,6 +8,7 @@
 #include <sys/types.h>
 #include <regex.h> /* POSIX.2 */
 #include <stdlib.h>
+#include <string.h>
 #include <unistd.h>
 
 #include "scheme48.h"