--- imap/src/mlock/mlock.c
+++ imap/src/mlock/mlock.c
@@ -32,6 +32,7 @@
 #include <netdb.h>
 #include <ctype.h>
 #include <strings.h>
+#include <string.h>
 
 #define LOCKTIMEOUT 5		/* lock timeout in minutes */
 #define LOCKPROTECTION 0775