diff --git a/bookwyrm/models/author.py b/bookwyrm/models/author.py
index 78d153a21..7d2a0e62b 100644
--- a/bookwyrm/models/author.py
+++ b/bookwyrm/models/author.py
@@ -42,6 +42,11 @@ class Author(BookDataModel):
                 for book in self.book_set.values_list("id", flat=True)
             ]
             cache.delete_many(cache_keys)
+
+        # normalize isni format
+        if self.isni:
+            self.isni = re.sub(r"\s", "", self.isni)
+
         return super().save(*args, **kwargs)
 
     @property