diff --git a/sandbox/add_version.sh b/sandbox/add_version.sh
index 7324335d..1c6d67ad 100755
--- a/sandbox/add_version.sh
+++ b/sandbox/add_version.sh
@@ -26,8 +26,15 @@ set -x
 
 mkdir "$cloud_functions_dir"
 cd "$cloud_functions_dir"
-echo "mypy==${version}
+case $version in
+  "basedmypy-"*)
+    echo "basedmypy==${version#basedmypy-}" > "requirements.in"
+    ;;
+  *)
+    echo "mypy==${version}
 typing-extensions" > "requirements.in"
+    ;;
+esac
 pip-compile
 ln -s ../main.py ./
 cd "$sandbox_dir"
diff --git a/sandbox/docker/basedmypy-latest b/sandbox/docker/basedmypy-latest
new file mode 120000
index 00000000..9eac6448
--- /dev/null
+++ b/sandbox/docker/basedmypy-latest
@@ -0,0 +1 @@
+basedmypy-2.1.0
\ No newline at end of file
diff --git a/sandbox/update_latest.sh b/sandbox/update_latest.sh
index 9b19da7d..47df75ed 100755
--- a/sandbox/update_latest.sh
+++ b/sandbox/update_latest.sh
@@ -10,11 +10,19 @@ fi
 
 set -u
 readonly version="$1"
+case $version in
+  basedmypy-*)
+    readonly latest=./basedmypy-latest
+    ;;
+  *)
+    readonly latest=./latest
+    ;;
+esac
 
 cd "${sandbox_dir}/cloud_functions"
-rm latest
-ln -s "$version" ./latest
+rm $latest
+ln -s "$version" $latest
 
 cd "${sandbox_dir}/docker"
-rm latest
-ln -s "$version" ./latest
+rm $latest
+ln -s "$version" $latest