diff --git a/winsup/cygwin/include/asm/socket.h b/winsup/cygwin/include/asm/socket.h
index 8c0132997..712a46092 100644
--- a/winsup/cygwin/include/asm/socket.h
+++ b/winsup/cygwin/include/asm/socket.h
@@ -22,6 +22,7 @@ details. */
 
 #define SIOCATMARK  _IOR('s',  7, long)  /* at oob mark? */
 #define FIONREAD    _IOR('f', 127, long) /* get # bytes to read */
+#define SIOCINQ     FIONREAD
 /* Compatible with termios.h */
 #define FIONBIO     0x8004667e		 /* set/clear non-blocking i/o */
 #define FIOASYNC    _IOW('f', 125, long) /* set/clear async i/o */