diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index bc5aaef..92274d2 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -47,3 +47,5 @@ jobs:
 
       - name: Ruff
         uses: chartboost/ruff-action@v1
+        with:
+          args: --select W
diff --git a/woltka/align.py b/woltka/align.py
index cee87e2..0ce7d29 100644
--- a/woltka/align.py
+++ b/woltka/align.py
@@ -70,7 +70,7 @@ def plain_mapper(fh, fmt=None, n=1000):
     target = n   # target line number at end of current chunk
 
     # parse alignment file
-    for i, (query, subject) in enumerate(parser(chain(iter(head), fh))):
+    for i, (query, subject) in enumerate(parser(chain(iter(head), fh))): 
 
         # add subject to subject set of the same query Id
         if query == this: