diff --git a/django/db/migrations/graph.py b/django/db/migrations/graph.py
index 1daa902162..4330c2b4a5 100644
--- a/django/db/migrations/graph.py
+++ b/django/db/migrations/graph.py
@@ -37,9 +37,9 @@ class MigrationGraph(object):
 
     def add_dependency(self, migration, child, parent):
         if child not in self.nodes:
-            raise KeyError("Migration %s dependencies references nonexistent child node %r" % (migration, child))
+            raise KeyError("Migration %s dependencies reference nonexistent child node %r" % (migration, child))
         if parent not in self.nodes:
-            raise KeyError("Migration %s dependencies references nonexistent parent node %r" % (migration, parent))
+            raise KeyError("Migration %s dependencies reference nonexistent parent node %r" % (migration, parent))
         self.dependencies.setdefault(child, set()).add(parent)
         self.dependents.setdefault(parent, set()).add(child)
 
diff --git a/tests/migrations/test_graph.py b/tests/migrations/test_graph.py
index 0e26f70cb6..3fcdd12667 100644
--- a/tests/migrations/test_graph.py
+++ b/tests/migrations/test_graph.py
@@ -174,7 +174,8 @@ class GraphTests(TestCase):
         graph.add_node(("app_b", "0001"), None)
         graph.add_dependency("app_a.0003", ("app_a", "0003"), ("app_a", "0002"))
         graph.add_dependency("app_a.0002", ("app_a", "0002"), ("app_a", "0001"))
-        with self.assertRaisesMessage(KeyError, "Migration app_a.0001 dependencies references nonexistent parent node ('app_b', '0002')"):
+        msg = "Migration app_a.0001 dependencies reference nonexistent parent node ('app_b', '0002')"
+        with self.assertRaisesMessage(KeyError, msg):
             graph.add_dependency("app_a.0001", ("app_a", "0001"), ("app_b", "0002"))
 
     def test_missing_child_nodes(self):
@@ -184,5 +185,6 @@ class GraphTests(TestCase):
         # Build graph
         graph = MigrationGraph()
         graph.add_node(("app_a", "0001"), None)
-        with self.assertRaisesMessage(KeyError, "Migration app_a.0002 dependencies references nonexistent child node ('app_a', '0002')"):
+        msg = "Migration app_a.0002 dependencies reference nonexistent child node ('app_a', '0002')"
+        with self.assertRaisesMessage(KeyError, msg):
             graph.add_dependency("app_a.0002", ("app_a", "0002"), ("app_a", "0001"))