diff --git a/scst/src/dev_handlers/scst_vdisk.c b/scst/src/dev_handlers/scst_vdisk.c
index 2ae1b0f46..f095817d2 100644
--- a/scst/src/dev_handlers/scst_vdisk.c
+++ b/scst/src/dev_handlers/scst_vdisk.c
@@ -1314,7 +1314,7 @@ static void vdisk_exec_unmap(struct scst_cmd *cmd, struct scst_vdisk_thr *thr)
 
 	TRACE_ENTRY();
 
-	if (unlikely(virt_dev->thin_provisioned)) {
+	if (unlikely(!virt_dev->thin_provisioned)) {
 		TRACE_DBG("%s", "Invalid opcode UNMAP");
 		scst_set_cmd_error(cmd,
 			SCST_LOAD_SENSE(scst_sense_invalid_opcode));