diff --git a/pylib/anki/collection.py b/pylib/anki/collection.py
index 2df64a6f9..296a1e74a 100644
--- a/pylib/anki/collection.py
+++ b/pylib/anki/collection.py
@@ -1010,7 +1010,9 @@ and type=0""",
         to_fix = []
         for id, tags in self.db.execute("select id, tags from notes"):
             norm = unicodedata.normalize("NFC", tags)
-            if not norm.startswith(" ") or not norm.endswith(" "):
+            if not norm.strip():
+                norm = ""
+            elif not norm.startswith(" ") or not norm.endswith(" "):
                 norm = " " + norm + " "
             if norm != tags:
                 to_fix.append((norm, self.usn(), intTime(), id))