diff --git a/OvmfPkg/XenBusDxe/Ia32/TestAndClearBit.S b/OvmfPkg/XenBusDxe/Ia32/TestAndClearBit.S
deleted file mode 100644
index 58dfa8ba57..0000000000
--- a/OvmfPkg/XenBusDxe/Ia32/TestAndClearBit.S
+++ /dev/null
@@ -1,13 +0,0 @@
-# INT32
-# EFIAPI
-# TestAndClearBit (
-#   IN  INT32 Bit,
-#   IN  volatile VOID* Address
-#   );
-ASM_GLOBAL ASM_PFX(TestAndClearBit)
-ASM_PFX(TestAndClearBit):
-  mov 4(%esp), %ecx
-  mov 8(%esp), %edx
-  lock btrl %ecx, (%edx)
-  sbbl %eax, %eax
-  ret
diff --git a/OvmfPkg/XenBusDxe/Ia32/TestAndClearBit.asm b/OvmfPkg/XenBusDxe/Ia32/TestAndClearBit.nasm
similarity index 67%
rename from OvmfPkg/XenBusDxe/Ia32/TestAndClearBit.asm
rename to OvmfPkg/XenBusDxe/Ia32/TestAndClearBit.nasm
index ac809020a6..d77f74ef24 100644
--- a/OvmfPkg/XenBusDxe/Ia32/TestAndClearBit.asm
+++ b/OvmfPkg/XenBusDxe/Ia32/TestAndClearBit.nasm
@@ -1,4 +1,4 @@
-.code
+SECTION .text
 
 ; INT32
 ; EFIAPI
@@ -6,12 +6,11 @@
 ;   IN  INT32 Bit,
 ;   IN  volatile VOID* Address
 ;   );
-TestAndClearBit PROC
+global ASM_PFX(TestAndClearBit)
+ASM_PFX(TestAndClearBit):
   mov ecx, [esp + 4]
   mov edx, [esp + 8]
   lock btr [edx], ecx
   sbb eax, eax
   ret
-TestAndClearBit ENDP
 
-END
diff --git a/OvmfPkg/XenBusDxe/XenBusDxe.inf b/OvmfPkg/XenBusDxe/XenBusDxe.inf
index 292e488387..b421b852e8 100644
--- a/OvmfPkg/XenBusDxe/XenBusDxe.inf
+++ b/OvmfPkg/XenBusDxe/XenBusDxe.inf
@@ -51,8 +51,7 @@
 [Sources.IA32]
   Ia32/hypercall.nasm
   Ia32/InterlockedCompareExchange16.nasm
-  Ia32/TestAndClearBit.S
-  Ia32/TestAndClearBit.asm
+  Ia32/TestAndClearBit.nasm
 
 [Sources.X64]
   X64/hypercall.S