diff --git a/contrib/pg_upgrade/option.c b/contrib/pg_upgrade/option.c
new file mode 100644
index e0a3c6d..2e7c347
*** a/contrib/pg_upgrade/option.c
--- b/contrib/pg_upgrade/option.c
*************** parseCommandLine(int argc, char *argv[])
*** 229,234 ****
--- 229,254 ----
  							 "PGDATAOLD", "-d", "old cluster data resides");
  	check_required_directory(&new_cluster.pgdata, &new_cluster.pgconfig,
  							 "PGDATANEW", "-D", "new cluster data resides");
+ 
+ #ifndef WIN32
+ 	/*
+ 	 * On Windows, initdb --sync-only will fail with a "Permission denied"
+ 	 * error on file pg_upgrade_utility.log if pg_upgrade is run inside
+ 	 * the new cluster directory, so we do a check here.
+ 	 */
+ 	{
+ 		char	cwd[MAXPGPATH], new_cluster_pgdata[MAXPGPATH];
+ 
+ 		strlcpy(new_cluster_pgdata, new_cluster.pgdata, MAXPGPATH);
+ 		canonicalize_path(new_cluster_pgdata);
+ 		
+ 		if (!getcwd(cwd, MAXPGPATH))
+ 			pg_fatal("cannot find current directory\n");
+ 		canonicalize_path(cwd);
+ 		if (path_is_prefix_of_path(new_cluster_pgdata, cwd))
+ 			pg_fatal("cannot run pg_upgrade from inside the new cluster data directory on Windows\n");
+ 	}
+ #endif
  }