diff --git a/main.lua b/main.lua
index 82c318f..f8b3343 100644
--- a/main.lua
+++ b/main.lua
@@ -656,6 +656,10 @@ end
 
 -- thruster is a thruster type, power is a vector from 0.0 to 1.0
 function SetThrusterPower(thruster, power)
+    if thruster == nil then
+        print("ERROR: SetThrusterPower called with nil thruster.")
+        return
+    end
     if thruster.type == "rotator" then
         thruster.power = power
         local actualPower = 0