Index: src/os_win.c
==================================================================
--- src/os_win.c
+++ src/os_win.c
@@ -5582,12 +5582,14 @@
 ** However if an error message is supplied, it will be incorporated
 ** by sqlite into the error message available to the user using
 ** sqlite3_errmsg(), possibly making IO errors easier to debug.
 */
 static int winGetLastError(sqlite3_vfs *pVfs, int nBuf, char *zBuf){
+  DWORD e = osGetLastError();
   UNUSED_PARAMETER(pVfs);
-  return winGetLastErrorMsg(osGetLastError(), nBuf, zBuf);
+  if( nBuf>0 ) winGetLastErrorMsg(e, nBuf, zBuf);
+  return e;
 }
 
 /*
 ** Initialize and deinitialize the operating system interface.
 */