diff --git a/bookwyrm/book_search.py b/bookwyrm/book_search.py
index 0dd41fccf..803641cb7 100644
--- a/bookwyrm/book_search.py
+++ b/bookwyrm/book_search.py
@@ -7,6 +7,7 @@ from django.contrib.postgres.search import SearchRank, SearchQuery
 from django.db.models import OuterRef, Subquery, F, Q
 
 from bookwyrm import models
+from bookwyrm import connectors
 from bookwyrm.settings import MEDIA_FULL_URL
 
 
@@ -74,6 +75,10 @@ def format_search_result(search_result):
 
 def search_identifiers(query, *filters, return_first=False):
     """tries remote_id, isbn; defined as dedupe fields on the model"""
+    if connectors.maybe_isbn(query):
+        # Oh did you think the 'S' in ISBN stood for 'standard'?
+        normalized_isbn = query.strip().upper().rjust(10, "0")
+        query = normalized_isbn
     # pylint: disable=W0212
     or_filters = [
         {f.name: query}
diff --git a/bookwyrm/connectors/__init__.py b/bookwyrm/connectors/__init__.py
index efbdb1666..3a4f5f3e0 100644
--- a/bookwyrm/connectors/__init__.py
+++ b/bookwyrm/connectors/__init__.py
@@ -1,6 +1,6 @@
 """ bring connectors into the namespace """
 from .settings import CONNECTORS
 from .abstract_connector import ConnectorException
-from .abstract_connector import get_data, get_image
+from .abstract_connector import get_data, get_image, maybe_isbn
 
 from .connector_manager import search, first_search_result
diff --git a/bookwyrm/connectors/abstract_connector.py b/bookwyrm/connectors/abstract_connector.py
index dce4e5089..c1ee7fe78 100644
--- a/bookwyrm/connectors/abstract_connector.py
+++ b/bookwyrm/connectors/abstract_connector.py
@@ -328,10 +328,10 @@ def maybe_isbn(query):
     """check if a query looks like an isbn"""
     isbn = re.sub(r"[\W_]", "", query)  # removes filler characters
     # ISBNs must be numeric except an ISBN10 checkdigit can be 'X'
-    if not isbn.rstrip("X").isnumeric():
+    if not isbn.upper().rstrip("X").isnumeric():
         return False
     return len(isbn) in [
         9,
         10,
         13,
-    ]  # ISBN10 or ISBN13, or maybe   ISBN10 missing a prepended zero
+    ]  # ISBN10 or ISBN13, or maybe ISBN10 missing a leading zero