diff --git a/src/calibre/gui2/preferences/search.py b/src/calibre/gui2/preferences/search.py
index d0264dfd2c..9ee4eec543 100644
--- a/src/calibre/gui2/preferences/search.py
+++ b/src/calibre/gui2/preferences/search.py
@@ -158,9 +158,9 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
             return error_dialog(self.gui, _('Grouped search terms'),
                                 _('The search term name cannot be blank'),
                                 show=True)
-        if ' ' in name:
+        if ' ' in name or '.' in name:
             return error_dialog(self.gui, _('Invalid grouped search name'),
-                _('The grouped search term name cannot contain spaces'), show=True)
+                _('The grouped search term name cannot contain spaces or periods'), show=True)
         if idx != 0:
             orig_name = str(self.gst_names.itemData(idx) or '')
         else: