diff --git a/src/axolotl/core/trainer_builder/rl.py b/src/axolotl/core/trainer_builder/rl.py
index f62e14880..e36af0f71 100644
--- a/src/axolotl/core/trainer_builder/rl.py
+++ b/src/axolotl/core/trainer_builder/rl.py
@@ -247,4 +247,4 @@ class HFPPOTrainerBuilder(TrainerBuilderBase):
 
     def build(self, total_num_steps):
         # build PPOConfig
-        pass
+        raise NotImplementedError("PPO trainer builder is not implemented yet.")