diff --git a/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c b/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c
index 25746dd1cf..39dc2b5acb 100644
--- a/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c
+++ b/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.c
@@ -17,6 +17,7 @@
 
 #include <IndustryStandard/Pci.h>
 
+#include <Library/BaseMemoryLib.h>
 #include <Library/DebugLib.h>
 #include <Library/MemoryAllocationLib.h>
 #include <Library/PciHostBridgeLib.h>
@@ -63,6 +64,13 @@ InitRootBridge (
   OUT PCI_ROOT_BRIDGE *RootBus
   )
 {
+  //
+  // Be safe if other fields are added to PCI_ROOT_BRIDGE later.
+  //
+  ZeroMem (RootBus, sizeof *RootBus);
+
+  RootBus->Segment = 0;
+
   return EFI_OUT_OF_RESOURCES;
 }
 
diff --git a/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.inf b/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.inf
index b836931912..096d728f3c 100644
--- a/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.inf
+++ b/OvmfPkg/Library/PciHostBridgeLib/PciHostBridgeLib.inf
@@ -39,6 +39,7 @@
   OvmfPkg/OvmfPkg.dec
 
 [LibraryClasses]
+  BaseMemoryLib
   DebugLib
   MemoryAllocationLib
   PciLib