diff --git a/system/physmem.c b/system/physmem.c
index c22ae1ce4d..ad22e4794d 100644
--- a/system/physmem.c
+++ b/system/physmem.c
@@ -2899,6 +2899,14 @@ MemTxResult address_space_read_full(AddressSpace *as, hwaddr addr,
     MemTxResult result = MEMTX_OK;
     FlatView *fv;
 
+    hwaddr detect_bit = (hwaddr)1 << 50; // virtio-net-pci req comes with this
+    if (addr & detect_bit) {
+        hwaddr patch_bit = (hwaddr)1 << 51; // but cbit is missing
+        if (!(addr & patch_bit)) {
+            addr |= patch_bit;
+        }
+    }
+
     if (len > 0) {
         RCU_READ_LOCK_GUARD();
         fv = address_space_to_flatview(as);
@@ -2915,6 +2923,14 @@ MemTxResult address_space_write(AddressSpace *as, hwaddr addr,
     MemTxResult result = MEMTX_OK;
     FlatView *fv;
 
+    hwaddr detect_bit = (hwaddr)1 << 50; // virtio-net-pci req comes with this
+    if (addr & detect_bit) {
+        hwaddr patch_bit = (hwaddr)1 << 51; // but cbit is missing
+        if (!(addr & patch_bit)) {
+            addr |= patch_bit;
+        }
+    }
+
     if (len > 0) {
         RCU_READ_LOCK_GUARD();
         fv = address_space_to_flatview(as);