diff --git a/plinth/modules/calibre/forms.py b/plinth/modules/calibre/forms.py
index 84c7e187e..378c43420 100644
--- a/plinth/modules/calibre/forms.py
+++ b/plinth/modules/calibre/forms.py
@@ -16,9 +16,9 @@ class CreateLibraryForm(forms.Form):
 
     name = forms.CharField(
         label=_('Name of the new library'), strip=True,
-        help_text=_('Only letters of the English alphabet and numbers, '
-                    'without spaces or special characters. Example: '
-                    'My_Library_2000'),
+        help_text=_('Only letters of the English alphabet, numbers '
+                    'and the characters _ . and - without spaces or '
+                    'special characters. Example: My_Library_2000'),
         validators=[validators.RegexValidator(r'^[A-Za-z0-9_.-]+$')])
 
     def clean_name(self):