diff --git a/src/calibre/gui2/tweak_book/editor/snippets.py b/src/calibre/gui2/tweak_book/editor/snippets.py
index e5114d4b4a..b9d1496583 100644
--- a/src/calibre/gui2/tweak_book/editor/snippets.py
+++ b/src/calibre/gui2/tweak_book/editor/snippets.py
@@ -23,7 +23,7 @@ from calibre.gui2.tweak_book.widgets import Dialog
 from calibre.utils.config import JSONConfig
 from calibre.utils.icu import string_length as strlen
 
-string_length = lambda x: strlen(unicode(x))
+string_length = lambda x: strlen(unicode(x))  # Needed on narrow python builds, as subclasses of unicode dont work
 
 SnipKey = namedtuple('SnipKey', 'trigger syntaxes')
 def snip_key(trigger, *syntaxes):