diff --git a/dll/win32/msi/action.c b/dll/win32/msi/action.c
index f7186446203..0640d9ae1c8 100644
--- a/dll/win32/msi/action.c
+++ b/dll/win32/msi/action.c
@@ -2005,7 +2005,7 @@ static WCHAR *create_temp_dir( MSIDATABASE *db )
  *  A \ will not be added after the last segment, however if the
  *  last segment is NULL, then the last character will be a \
  */
-WCHAR *msi_build_directory_name( DWORD count, ... )
+WCHAR * WINAPIV msi_build_directory_name( DWORD count, ... )
 {
     DWORD sz = 1, i;
     WCHAR *dir;
diff --git a/dll/win32/msi/msipriv.h b/dll/win32/msi/msipriv.h
index e3b808db89a..6da8203b721 100644
--- a/dll/win32/msi/msipriv.h
+++ b/dll/win32/msi/msipriv.h
@@ -1039,7 +1039,7 @@ extern MSIFOLDER *msi_get_loaded_folder(MSIPACKAGE *package, const WCHAR *dir) D
 extern WCHAR *msi_create_temp_file(MSIDATABASE *db) DECLSPEC_HIDDEN;
 extern void msi_free_action_script(MSIPACKAGE *package, UINT script) DECLSPEC_HIDDEN;
 extern WCHAR *msi_build_icon_path(MSIPACKAGE *, const WCHAR *) DECLSPEC_HIDDEN;
-extern WCHAR *msi_build_directory_name(DWORD , ...) DECLSPEC_HIDDEN;
+extern WCHAR * WINAPIV msi_build_directory_name(DWORD , ...) DECLSPEC_HIDDEN;
 extern void msi_reduce_to_long_filename(WCHAR *) DECLSPEC_HIDDEN;
 extern WCHAR *msi_create_component_advertise_string(MSIPACKAGE *, MSICOMPONENT *, const WCHAR *) DECLSPEC_HIDDEN;
 extern void ACTION_UpdateComponentStates(MSIPACKAGE *package, MSIFEATURE *feature) DECLSPEC_HIDDEN;