diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 4d6bcbb846..f8b919cb6c 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -81,7 +81,9 @@
     { "qemu64-" TYPE_X86_CPU, "model-id", "QEMU Virtual CPU version " v, },\
     { "athlon-" TYPE_X86_CPU, "model-id", "QEMU Virtual CPU version " v, },
 
-GlobalProperty pc_compat_10_1[] = {};
+GlobalProperty pc_compat_10_1[] = {
+    { "mch", "extended-tseg-mbytes", "16" },
+};
 const size_t pc_compat_10_1_len = G_N_ELEMENTS(pc_compat_10_1);
 
 GlobalProperty pc_compat_10_0[] = {
diff --git a/hw/pci-host/q35.c b/hw/pci-host/q35.c
index 1951ae440c..a708758d36 100644
--- a/hw/pci-host/q35.c
+++ b/hw/pci-host/q35.c
@@ -663,7 +663,7 @@ static void mch_realize(PCIDevice *d, Error **errp)
 
 static const Property mch_props[] = {
     DEFINE_PROP_UINT16("extended-tseg-mbytes", MCHPCIState, ext_tseg_mbytes,
-                       16),
+                       64),
     DEFINE_PROP_BOOL("smbase-smram", MCHPCIState, has_smram_at_smbase, true),
 };