diff --git a/OvmfPkg/Csm/CsmSupportLib/CsmSupportLib.inf b/OvmfPkg/Csm/CsmSupportLib/CsmSupportLib.inf
index ba050cbb4f..f61a22f8ff 100644
--- a/OvmfPkg/Csm/CsmSupportLib/CsmSupportLib.inf
+++ b/OvmfPkg/Csm/CsmSupportLib/CsmSupportLib.inf
@@ -32,6 +32,7 @@
   CsmSupportLib.c
   CsmSupportLib.h
   LegacyInterrupt.c
+  LegacyInterrupt.h
   LegacyPlatform.c
   LegacyRegion.c