diff --git a/examples/advanced/1_train_act_pusht/act_pusht.yaml b/examples/advanced/1_train_act_pusht/act_pusht.yaml
index 38e542fb4..d56a4ac5b 100644
--- a/examples/advanced/1_train_act_pusht/act_pusht.yaml
+++ b/examples/advanced/1_train_act_pusht/act_pusht.yaml
@@ -28,7 +28,7 @@ training:
   online_steps_between_rollouts: 1
 
   delta_timestamps:
-    action: "[i / ${fps} for i in range(${policy.chunk_size})]"
+    action: "[i / ${fps} for i in range(1, ${policy.chunk_size} + 1)]"
 
 eval:
   n_episodes: 50
diff --git a/lerobot/configs/policy/act.yaml b/lerobot/configs/policy/act.yaml
index bba2e5638..bf6e59e99 100644
--- a/lerobot/configs/policy/act.yaml
+++ b/lerobot/configs/policy/act.yaml
@@ -25,7 +25,7 @@ training:
   online_steps_between_rollouts: 1
 
   delta_timestamps:
-    action: "[i / ${fps} for i in range(${policy.chunk_size})]"
+    action: "[i / ${fps} for i in range(1, ${policy.chunk_size} + 1)]"
 
 eval:
   n_episodes: 50
diff --git a/lerobot/configs/policy/act_real.yaml b/lerobot/configs/policy/act_real.yaml
index b49426152..8b1f280c4 100644
--- a/lerobot/configs/policy/act_real.yaml
+++ b/lerobot/configs/policy/act_real.yaml
@@ -51,7 +51,7 @@ training:
   online_steps_between_rollouts: 1
 
   delta_timestamps:
-    action: "[i / ${fps} for i in range(${policy.chunk_size})]"
+    action: "[i / ${fps} for i in range(1, ${policy.chunk_size} + 1)]"
 
 eval:
   n_episodes: 50
diff --git a/lerobot/configs/policy/act_real_no_state.yaml b/lerobot/configs/policy/act_real_no_state.yaml
index a8b1c9b6c..dc2459a19 100644
--- a/lerobot/configs/policy/act_real_no_state.yaml
+++ b/lerobot/configs/policy/act_real_no_state.yaml
@@ -49,7 +49,7 @@ training:
   online_steps_between_rollouts: 1
 
   delta_timestamps:
-    action: "[i / ${fps} for i in range(${policy.chunk_size})]"
+    action: "[i / ${fps} for i in range(1, ${policy.chunk_size} + 1)]"
 
 eval:
   n_episodes: 50