diff --git a/src/calibre/ebooks/metadata/sources/amazon.py b/src/calibre/ebooks/metadata/sources/amazon.py
index 27932b9a2b..8b08efa66e 100644
--- a/src/calibre/ebooks/metadata/sources/amazon.py
+++ b/src/calibre/ebooks/metadata/sources/amazon.py
@@ -879,6 +879,8 @@ class Amazon(Source):
         if mi.tags and docase:
             mi.tags = list(map(fixcase, mi.tags))
         mi.isbn = check_isbn(mi.isbn)
+        if mi.series and docase:
+            mi.series = fixcase(mi.series)
 
     def get_website_domain(self, domain):
         udomain = domain