diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index c09359d..37de017 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -290,6 +290,12 @@
 	unsigned short logical_block_size = queue_logical_block_size(q);
 	sector_t num_sectors;
 
+	/* Reject unsupported discard requests */
+	if ((rw & REQ_DISCARD) && !blk_queue_discard(q)) {
+		dec_count(io, region, -EOPNOTSUPP);
+		return;
+	}
+
 	/*
 	 * where->count may be zero if rw holds a flush and we need to
 	 * send a zero-sized flush.