diff --git a/action.yml b/action.yml
index 0d9d9a9..e4a394d 100644
--- a/action.yml
+++ b/action.yml
@@ -20,7 +20,8 @@ runs:
   using: composite
   steps:
     - name: Install uv
-      uses: astral-sh/setup-uv@v6
+      # Immutable pin for astral-sh/setup-uv v6.
+      uses: astral-sh/setup-uv@d0cc045d04ccac9d8b7881df0226f9e82c39688e
       with:
         enable-cache: true