diff --git a/sqlalchemy_utils/functions/foreign_keys.py b/sqlalchemy_utils/functions/foreign_keys.py
index e1da428..81cd782 100644
--- a/sqlalchemy_utils/functions/foreign_keys.py
+++ b/sqlalchemy_utils/functions/foreign_keys.py
@@ -357,9 +357,9 @@ def is_indexed_foreign_key(constraint):
     :param constraint: ForeignKeyConstraint object to check the indexes
     """
     return any(
-        set(column.name for column in index.columns)
+        set(constraint.columns.keys())
         ==
-        set(constraint.columns)
+        set(column.name for column in index.columns)
         for index
         in constraint.table.indexes
     )
diff --git a/tests/functions/test_non_indexed_foreign_keys.py b/tests/functions/test_non_indexed_foreign_keys.py
index 4f8a30e..3c1791e 100644
--- a/tests/functions/test_non_indexed_foreign_keys.py
+++ b/tests/functions/test_non_indexed_foreign_keys.py
@@ -1,3 +1,5 @@
+from itertools import chain
+
 import sqlalchemy as sa
 
 from sqlalchemy_utils.functions import non_indexed_foreign_keys
@@ -43,8 +45,13 @@ class TestFindNonIndexedForeignKeys(TestCase):
             'article' in
             fks
         )
-        column_names = [
-            column_name for column_name in fks['article'][0].columns.keys()
-        ]
+        column_names = list(chain(
+            *(
+                names for names in (
+                    fk.columns.keys()
+                    for fk in fks['article']
+                )
+            )
+        ))
         assert 'category_id' in column_names
         assert 'author_id' not in column_names