diff --git a/OvmfPkg/Include/Library/QemuBootOrderLib.h b/OvmfPkg/Include/Library/QemuBootOrderLib.h
index 743a717824..874344a95d 100644
--- a/OvmfPkg/Include/Library/QemuBootOrderLib.h
+++ b/OvmfPkg/Include/Library/QemuBootOrderLib.h
@@ -49,6 +49,7 @@
 
 **/
 RETURN_STATUS
+EFIAPI
 SetBootOrderFromQemu (
   VOID
   );
@@ -61,6 +62,7 @@ SetBootOrderFromQemu (
   @return  The TimeoutDefault argument for PlatformBdsEnterFrontPage().
 **/
 UINT16
+EFIAPI
 GetFrontPageTimeoutFromQemu (
   VOID
   );
diff --git a/OvmfPkg/Library/QemuBootOrderLib/QemuBootOrderLib.c b/OvmfPkg/Library/QemuBootOrderLib/QemuBootOrderLib.c
index 682cc7a4dc..b699970b12 100644
--- a/OvmfPkg/Library/QemuBootOrderLib/QemuBootOrderLib.c
+++ b/OvmfPkg/Library/QemuBootOrderLib/QemuBootOrderLib.c
@@ -1763,6 +1763,7 @@ PruneBootVariables (
 
 **/
 RETURN_STATUS
+EFIAPI
 SetBootOrderFromQemu (
   VOID
   )
@@ -1946,6 +1947,7 @@ ErrorFreeFwCfg:
   @return  The TimeoutDefault argument for PlatformBdsEnterFrontPage().
 **/
 UINT16
+EFIAPI
 GetFrontPageTimeoutFromQemu (
   VOID
   )