diff --git a/src/storage_backend.c b/src/storage_backend.c
index 07a2e487d2..8824218e12 100644
--- a/src/storage_backend.c
+++ b/src/storage_backend.c
@@ -446,7 +446,7 @@ virStorageBackendCreateQemuImg(virConnectPtr conn,
 
 
     /* Size in KB */
-    snprintf(size, sizeof(size), "%llu", vol->capacity/1024);
+    snprintf(size, sizeof(size), "%lluK", vol->capacity/1024);
 
     if (virRun(conn, imgargv, NULL) < 0) {
         VIR_FREE(imgargv[0]);