diff --git a/sysdeps/unix/sysv/linux/bits/in.h b/sysdeps/unix/sysv/linux/bits/in.h
index 6bf2fded21..8f3aca4ba1 100644
--- a/sysdeps/unix/sysv/linux/bits/in.h
+++ b/sysdeps/unix/sysv/linux/bits/in.h
@@ -129,6 +129,7 @@
 #define IP_MULTICAST_ALL		49
 #define IP_UNICAST_IF			50
 #define IP_LOCAL_PORT_RANGE		51
+#define IP_PROTOCOL			52
 
 /* To select the IP level.  */
 #define SOL_IP	0