diff --git a/beets/dbcore/db.py b/beets/dbcore/db.py
index fd6dd0c10..7fbf646dc 100755
--- a/beets/dbcore/db.py
+++ b/beets/dbcore/db.py
@@ -29,6 +29,7 @@ from sqlite3 import Connection
 from types import TracebackType
 from typing import (
     Any,
+    AnyStr,
     Callable,
     DefaultDict,
     Dict,
@@ -1088,8 +1089,22 @@ class Database:
                 value = value.decode()
             return re.search(pattern, str(value)) is not None
 
+        def bytelower(bytestring: Optional[AnyStr]) -> Optional[AnyStr]:
+            """A custom ``bytelower`` sqlite function so we can compare
+            bytestrings in a semi case insensitive fashion.
+
+            This is to work around sqlite builds are that compiled with
+            ``-DSQLITE_LIKE_DOESNT_MATCH_BLOBS``. See
+            ``https://github.com/beetbox/beets/issues/2172`` for details.
+            """
+            if bytestring is not None:
+                return bytestring.lower()
+
+            return bytestring
+
         conn.create_function("regexp", 2, regexp)
         conn.create_function("unidecode", 1, unidecode)
+        conn.create_function("bytelower", 1, bytelower)
 
     def _close(self):
         """Close the all connections to the underlying SQLite database
diff --git a/beets/library.py b/beets/library.py
index 754583f57..367b184ef 100644
--- a/beets/library.py
+++ b/beets/library.py
@@ -1550,17 +1550,6 @@ def parse_query_string(s, model_cls):
     return parse_query_parts(parts, model_cls)
 
 
-def _sqlite_bytelower(bytestring):
-    """A custom ``bytelower`` sqlite function so we can compare
-    bytestrings in a semi case insensitive fashion.
-
-    This is to work around sqlite builds are that compiled with
-    ``-DSQLITE_LIKE_DOESNT_MATCH_BLOBS``. See
-    ``https://github.com/beetbox/beets/issues/2172`` for details.
-    """
-    return bytestring.lower()
-
-
 # The Library: interface to the database.
 
 
@@ -1585,11 +1574,6 @@ class Library(dbcore.Database):
 
         self._memotable = {}  # Used for template substitution performance.
 
-    def _create_connection(self):
-        conn = super()._create_connection()
-        conn.create_function("bytelower", 1, _sqlite_bytelower)
-        return conn
-
     # Adding objects to the database.
 
     def add(self, obj):