diff --git a/hw/pci.c b/hw/pci.c
index a326930..6864339 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -856,9 +856,9 @@
     int i;
     uint32_t config_size = pci_config_size(d);
 
-    for(i = 0; i < l && addr < config_size; val >>= 8, ++i, ++addr) {
-        uint8_t wmask = d->wmask[addr];
-        d->config[addr] = (d->config[addr] & ~wmask) | (val & wmask);
+    for (i = 0; i < l && addr + i < config_size; val >>= 8, ++i) {
+        uint8_t wmask = d->wmask[addr + i];
+        d->config[addr + i] = (d->config[addr + i] & ~wmask) | (val & wmask);
     }
     if (ranges_overlap(addr, l, PCI_BASE_ADDRESS_0, 24) ||
         ranges_overlap(addr, l, PCI_ROM_ADDRESS, 4) ||