diff --git a/src/core/sys/windows/windows.d b/src/core/sys/windows/windows.d
index ddc2330488b..2757e850576 100644
--- a/src/core/sys/windows/windows.d
+++ b/src/core/sys/windows/windows.d
@@ -3932,6 +3932,7 @@ BOOL LockFile(HANDLE hFile, DWORD dwFileOffsetLow, DWORD dwFileOffsetHigh, DWORD
 BOOL UnlockFile(HANDLE hFile, DWORD dwFileOffsetLow, DWORD dwFileOffsetHigh, DWORD nNumberOfBytesToUnlockLow, DWORD nNumberOfBytesToUnlockHigh);
 BOOL LockFileEx(HANDLE hFile, DWORD dwFlags, DWORD dwReserved, DWORD nNumberOfBytesToLockLow, DWORD nNumberOfBytesToLockHigh, LPOVERLAPPED lpOverlapped);
 BOOL UnlockFileEx(HANDLE hFile, DWORD dwReserved, DWORD nNumberOfBytesToUnlockLow, DWORD nNumberOfBytesToUnlockHigh, LPOVERLAPPED lpOverlapped);
+BOOL FlushFileBuffers(HANDLE hFile);
 }
 
 enum LOCKFILE_FAIL_IMMEDIATELY = 1;