diff --git a/fsipd.c b/fsipd.c
index 35b3a0b..291aecc 100644
--- a/fsipd.c
+++ b/fsipd.c
@@ -33,6 +33,7 @@
 #include <netdb.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
+#include <ctype.h>
 
 #include <err.h>
 #include <errno.h>