diff --git a/OvmfPkg/Library/AcpiTimerLib/AcpiTimerLib.c b/OvmfPkg/Library/AcpiTimerLib/AcpiTimerLib.c
index 027912e0f7..8f4a5b3d1e 100644
--- a/OvmfPkg/Library/AcpiTimerLib/AcpiTimerLib.c
+++ b/OvmfPkg/Library/AcpiTimerLib/AcpiTimerLib.c
@@ -60,7 +60,7 @@ AcpiTimerLibConstructor (
     mPmba = PcdGet16 (PcdAcpiPmBaseAddress);
 
     PciAndThenOr32 (PCI_LIB_ADDRESS (0,Device,3,0x40),
-                    (UINT32) ~0xfc0, mPmba);
+                    (UINT32) ~0xFFC0, mPmba);
     PciOr8         (PCI_LIB_ADDRESS (0,Device,3,0x04), 0x01);
   }
 
diff --git a/OvmfPkg/PlatformPei/Platform.c b/OvmfPkg/PlatformPei/Platform.c
index d91f113693..589c5c3804 100644
--- a/OvmfPkg/PlatformPei/Platform.c
+++ b/OvmfPkg/PlatformPei/Platform.c
@@ -230,7 +230,7 @@ MiscInitialization (
     //
     // Set the PM I/O base address to 0x400
     //
-    PciAndThenOr32 (PCI_LIB_ADDRESS (0, 1, 3, 0x40), (UINT32) ~0xfc0, 0x400);
+    PciAndThenOr32 (PCI_LIB_ADDRESS (0, 1, 3, 0x40), (UINT32) ~0xFFC0, 0x400);
   }
 }