diff --git a/NEWS b/NEWS
index 572b350d..d5b787a3 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,5 @@
+  - use tempnam() instead of unqid() to create better temporary files in
+    smarty_core_write_file() (xces, messju)
   - add 'mail' to escape modifier for safe display of e-mail
     addresses (Monte)
   - add cycle function attribute "reset" to english docs (Monte)
diff --git a/libs/core/core.write_file.php b/libs/core/core.write_file.php
index b4fa92e5..d6de7311 100644
--- a/libs/core/core.write_file.php
+++ b/libs/core/core.write_file.php
@@ -25,7 +25,7 @@ function smarty_core_write_file($params, &$smarty)
 
     // write to tmp file, then rename it to avoid
     // file locking race condition
-    $_tmp_file = $_dirname . DIRECTORY_SEPARATOR . uniqid('');
+    $_tmp_file = tempnam($_dirname, 'write_');
 
     if (!($fd = @fopen($_tmp_file, 'w'))) {
         $smarty->trigger_error("problem writing temporary file '$_tmp_file'");
@@ -33,11 +33,16 @@ function smarty_core_write_file($params, &$smarty)
     }
 
     fwrite($fd, $params['contents']);
+
+    // Set the file's mtime
     if (isset($params['timestamp'])) {
        touch($_tmp_file, $params['timestamp']);
     }
     fclose($fd);
-    if(file_exists($params['filename'])) {
+
+    // Delete the file if it allready exists (this is needed on Win,
+    // because it cannot overwrite files with rename()
+    if (file_exists($params['filename'])) {
         @unlink($params['filename']);
     }
     @rename($_tmp_file, $params['filename']);