diff --git a/hw/vfio/igd.c b/hw/vfio/igd.c
index 4047f4f071..73ed1ec8e6 100644
--- a/hw/vfio/igd.c
+++ b/hw/vfio/igd.c
@@ -268,7 +268,7 @@ static int vfio_igd_gtt_max(VFIOPCIDevice *vdev)
 
     gmch = vfio_pci_read_config(&vdev->pdev, IGD_GMCH, sizeof(gmch));
     ggms = (gmch >> (gen < 8 ? 8 : 6)) & 0x3;
-    if (gen > 6) {
+    if (gen > 6 && ggms != 0) {
         ggms = 1 << ggms;
     }
 
@@ -678,7 +678,7 @@ void vfio_probe_igd_bar4_quirk(VFIOPCIDevice *vdev, int nr)
 
     /* Determine the size of stolen memory needed for GTT */
     ggms_mb = (gmch >> (gen < 8 ? 8 : 6)) & 0x3;
-    if (gen > 6) {
+    if (gen > 6 && ggms_mb != 0) {
         ggms_mb = 1 << ggms_mb;
     }