diff --git a/hw/pass-through.c b/hw/pass-through.c
index 3a1c8c4..1ac1c4c 100644
--- a/hw/pass-through.c
+++ b/hw/pass-through.c
@@ -1099,7 +1099,8 @@ static void pt_pci_write_config(PCIDevice *d, uint32_t address, uint32_t val,
     if (reg_grp_entry == NULL)
         goto out;
 
-    /* adjust the write value to appropriate CFC-CFF window */
+    /* adjust the read and write value to appropriate CFC-CFF window */
+    read_val <<= ((address & 3) << 3);
     val <<= ((address & 3) << 3);
     emul_len = len;