diff --git a/libc/include/netinet/in_systm.h b/libc/include/netinet/in_systm.h
index ff53fb7..7e474ba 100644
--- a/libc/include/netinet/in_systm.h
+++ b/libc/include/netinet/in_systm.h
@@ -34,6 +34,8 @@
 #ifndef _NETINET_IN_SYSTM_H_
 #define _NETINET_IN_SYSTM_H_
 
+#include <sys/types.h>
+
 /*
  * Miscellaneous internetwork
  * definitions for kernel.