diff --git a/winsup/cygwin/include/asm/socket.h b/winsup/cygwin/include/asm/socket.h
index 712a46092..9aeb889b8 100644
--- a/winsup/cygwin/include/asm/socket.h
+++ b/winsup/cygwin/include/asm/socket.h
@@ -58,6 +58,7 @@ details. */
 #define SO_OOBINLINE    0x0100          /* leave received OOB data in line */
 #define SO_DONTLINGER   (unsigned int)(~SO_LINGER)
 #define SO_PEERCRED	0x0200		/* same as getpeereid */
+#define SO_PASSCRED	0x0400		/* enable receiving of credentials */
 
 /*
  * Additional options.
diff --git a/winsup/cygwin/include/cygwin/socket.h b/winsup/cygwin/include/cygwin/socket.h
index 15e132738..79c925948 100644
--- a/winsup/cygwin/include/cygwin/socket.h
+++ b/winsup/cygwin/include/cygwin/socket.h
@@ -107,7 +107,8 @@ struct cmsghdr
 	((unsigned char *) ((struct cmsghdr *)(cmsg) + 1))
 
 /* "Socket"-level control message types: */
-#define	SCM_RIGHTS	0x01		/* access rights (array of int) */
+#define	SCM_RIGHTS	0x01		/* descriptor passing (array of int) */
+#define	SCM_CREDENTIALS	0x02		/* credential passing (struct ucred) */
 
 #ifdef __INSIDE_CYGWIN__
 /* Definition of struct msghdr up to release 1.5.18 */