diff --git a/OvmfPkg/PlatformPei/Platform.c b/OvmfPkg/PlatformPei/Platform.c
index 5e0a154842..9c013613a1 100644
--- a/OvmfPkg/PlatformPei/Platform.c
+++ b/OvmfPkg/PlatformPei/Platform.c
@@ -181,6 +181,7 @@ MemMapInitialization (
 
     TopOfLowRam = GetSystemMemorySizeBelow4gb ();
     PciExBarBase = 0;
+    PciBase = (TopOfLowRam < BASE_2GB) ? BASE_2GB : TopOfLowRam;
     if (mHostBridgeDevId == INTEL_Q35_MCH_DEVICE_ID) {
       //
       // The MMCONFIG area is expected to fall between the top of low RAM and
@@ -192,7 +193,6 @@ MemMapInitialization (
       PciBase = (UINT32)(PciExBarBase + SIZE_256MB);
       PciSize = 0xFC000000 - PciBase;
     } else {
-      PciBase = (TopOfLowRam < BASE_2GB) ? BASE_2GB : TopOfLowRam;
       PciSize = 0xFC000000 - PciBase;
     }