diff --git a/include/sys/dkio.h b/include/sys/dkio.h
index 0659e90825..591fbf51d0 100644
--- a/include/sys/dkio.h
+++ b/include/sys/dkio.h
@@ -33,5 +33,6 @@ struct dk_callback {
 
 #define	DKIOC			(0x04 << 8)
 #define	DKIOCFLUSHWRITECACHE	(DKIOC | 34)
+#define	DKIOCTRIM		(DKIOC | 35)
 
 #endif /* _SPL_DKIO_H */