diff --git a/requirements-test.txt b/requirements-test.txt
index 4c209f9..c869a92 100644
--- a/requirements-test.txt
+++ b/requirements-test.txt
@@ -1,6 +1,6 @@
 -e .
 iso8601>=0.1.12
-mypy==0.990
+mypy==0.991
 mypy-extensions==0.4.3
 pre-commit==2.20.0
 pytest==7.2.0