diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 84b33216..a48c4fd3 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -11,10 +11,10 @@ jobs:
     if: github.event.pull_request.draft == false
     steps:
       - uses: actions/checkout@v2
-      - name: Set up Python 3.8
+      - name: Set up Python 3.9
         uses: actions/setup-python@v1
         with:
-          python-version: 3.8
+          python-version: 3.9
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
diff --git a/nnabla_rl/model_trainers/v_value/v_function_trainer.py b/nnabla_rl/model_trainers/v_value/v_function_trainer.py
index 279de65b..3641f797 100644
--- a/nnabla_rl/model_trainers/v_value/v_function_trainer.py
+++ b/nnabla_rl/model_trainers/v_value/v_function_trainer.py
@@ -114,7 +114,7 @@ def _build_one_step_graph(
         target_v = self._compute_target(training_variables)
         target_v.need_grad = False
 
-        loss = 0
+        loss = 0.0
         for v_function in models:
             v_function = cast(VFunction, v_function)
             v_loss = self._compute_loss(v_function, target_v, training_variables)