diff --git a/src/calibre/gui2/dialogs/config/save_template.py b/src/calibre/gui2/dialogs/config/save_template.py
index 8fe36c430f..71eb15f4aa 100644
--- a/src/calibre/gui2/dialogs/config/save_template.py
+++ b/src/calibre/gui2/dialogs/config/save_template.py
@@ -37,7 +37,7 @@ class SaveTemplate(QWidget, Ui_Form):
         tmpl = preprocess_template(self.opt_template.text())
         fa = {}
         for x in FORMAT_ARG_DESCS.keys():
-            fa[x]=''
+            fa[x]='random long string'
         try:
             tmpl.format(**fa)
         except Exception, err: