diff --git a/src/_pytest/main.py b/src/_pytest/main.py
index 79a24632b..ca2b976b2 100644
--- a/src/_pytest/main.py
+++ b/src/_pytest/main.py
@@ -232,6 +232,7 @@ def pytest_addoption(parser: Parser) -> None:
         "--tmp-path-retention-count",
         dest="tmp_path_retention_count",
         default=3,
+        type="int",
         metavar="num",
         help="How many sessions should we keep the `tmp_path` directories, according to `tmp_path_retention_policy`.",
     )