diff --git a/picard/formats/vorbis.py b/picard/formats/vorbis.py
index 2d8cee10f..ca4081000 100644
--- a/picard/formats/vorbis.py
+++ b/picard/formats/vorbis.py
@@ -53,6 +53,10 @@ INVALID_CHARS = re.compile('([^\x20-}]|=)')
 
 
 def sanitize_key(key):
+    """
+    Remove characters from key which are invalid for a Vorbis comment field name.
+    See https://www.xiph.org/vorbis/doc/v-comment.html#vectorformat
+    """
     return INVALID_CHARS.sub('', key)
 
 
diff --git a/test/test_formats.py b/test/test_formats.py
index 005dccfec..a06981830 100644
--- a/test/test_formats.py
+++ b/test/test_formats.py
@@ -19,7 +19,7 @@ from picard.coverart.image import (
     TagCoverArtImage,
 )
 import picard.formats
-from picard.formats import ext_to_format
+from picard.formats import ext_to_format, vorbis
 from picard.metadata import Metadata
 
 settings = {
@@ -609,6 +609,12 @@ class OptimFROGDUalStreamTest(CommonTests.FormatsTest):
         self.assertEqual(metadata['~format'], 'OptimFROG DualStream Audio')
 
 
+class VorbisUtilTest(PicardTestCase):
+    def test_sanitize_key(self):
+        sanitized = vorbis.sanitize_key(' \x1f=}~')
+        self.assertEqual(sanitized, ' }')
+
+
 cover_settings = {
     'embed_only_one_front_image': True,
 }