diff --git a/simulation/simulation_resources/scripts/gz_step.py b/simulation/simulation_resources/scripts/gz_step.py
index b3e29c5d..51835d54 100644
--- a/simulation/simulation_resources/scripts/gz_step.py
+++ b/simulation/simulation_resources/scripts/gz_step.py
@@ -3,6 +3,7 @@
     python3 gz_step.py --step_sec 1.0
 """
 import os
+import math
 import argparse
 import gz.transport13
 from gz.msgs10.world_control_pb2 import WorldControl
@@ -11,9 +12,11 @@
 
 def main():
     parser = argparse.ArgumentParser(description='Control Gazebo world simulation stepping')
-    parser.add_argument('--step_sec', type=float, help='Number of seconds to advance the simulation')
+    parser.add_argument('--step_sec', type=float, required=True, help='Number of seconds to advance the simulation (must be > 0)')
     args = parser.parse_args()
-    
+    if args.step_sec is None or not math.isfinite(args.step_sec) or args.step_sec <= 0:
+        parser.error('--step_sec must be a finite number greater than 0')
+
     world_name = os.environ.get('WORLD', 'default')
     autopilot = os.environ.get('AUTOPILOT', 'px4')
 
@@ -24,6 +27,9 @@ def main():
         req.multi_step = int(args.step_sec * 250) # PX4 SDF worlds use 250 steps per simulation step (4ms)
     elif autopilot == 'ardupilot':
         req.multi_step = int(args.step_sec * 500) # ArduPilot SDF worlds use 500 steps per simulation step (2ms)
+    else:
+        print(f"Unsupported AUTOPILOT={autopilot!r}; expected px4 or ardupilot")
+        return
     req.pause = True # Stops the simulation after the step
 
     result, response = gz_node.request(