diff --git a/Source/Windows/Common/CRT/IO.cpp b/Source/Windows/Common/CRT/IO.cpp
index 79083e61f..af291ef3c 100644
--- a/Source/Windows/Common/CRT/IO.cpp
+++ b/Source/Windows/Common/CRT/IO.cpp
@@ -352,10 +352,18 @@ int getc(FILE* _File) {
   UNIMPLEMENTED();
 }
 
+void _lock_file(FILE* _File) {
+  UNIMPLEMENTED();
+}
+
 wint_t ungetwc(wint_t _Ch, FILE* _File) {
   UNIMPLEMENTED();
 }
 
+void _unlock_file(FILE* _File) {
+  UNIMPLEMENTED();
+}
+
 DLLEXPORT_FUNC(FILE*, __acrt_iob_func, (unsigned index)) {
   return nullptr;
 }