diff --git a/examples/pybullet/gym/pybullet_envs/deep_mimic/DeepMimic_Optimizer.py b/examples/pybullet/gym/pybullet_envs/deep_mimic/DeepMimic_Optimizer.py
index 31a23688c..196e251b2 100644
--- a/examples/pybullet/gym/pybullet_envs/deep_mimic/DeepMimic_Optimizer.py
+++ b/examples/pybullet/gym/pybullet_envs/deep_mimic/DeepMimic_Optimizer.py
@@ -20,6 +20,7 @@ world = None
 def run():
   global update_timestep
   global world
+  done = False
   while not (done):
     update_world(world, update_timestep)