diff --git a/mshow.c b/mshow.c
index 62f2b94..987f4e4 100644
--- a/mshow.c
+++ b/mshow.c
@@ -9,6 +9,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <time.h>
 #include <unistd.h>
 
diff --git a/msort.c b/msort.c
index 28b0fbc..0a1848d 100644
--- a/msort.c
+++ b/msort.c
@@ -5,6 +5,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <time.h>
 #include <unistd.h>
 
diff --git a/rfc2045.c b/rfc2045.c
index 4738894..1d853ab 100644
--- a/rfc2045.c
+++ b/rfc2045.c
@@ -1,5 +1,6 @@
 #include <sys/types.h>
 
+#include <strings.h>
 #include <string.h>
 
 #include "blaze822.h"