diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 528b189352..94b2919f52 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -1782,6 +1782,8 @@ qemuBuildRBDString(virConnectPtr conn,
                             disk->auth.username);
             goto error;
         }
+    } else {
+        virBufferAddLit(opt, ":auth_supported=none");
     }
 
     if (disk->nhosts > 0) {