diff --git a/hw/ppc/pnv_pnor.c b/hw/ppc/pnv_pnor.c
index 5ef1cf2afb..83ecccca28 100644
--- a/hw/ppc/pnv_pnor.c
+++ b/hw/ppc/pnv_pnor.c
@@ -36,7 +36,7 @@ static void pnv_pnor_update(PnvPnor *s, int offset, int size)
     int offset_end;
     int ret;
 
-    if (s->blk) {
+    if (!s->blk || !blk_is_writable(s->blk)) {
         return;
     }