diff --git a/python/JSBSim.py b/python/JSBSim.py
index 93166cfd4d..d3a195ab1a 100644
--- a/python/JSBSim.py
+++ b/python/JSBSim.py
@@ -125,7 +125,7 @@ def CheckXMLFile(f):
 
 args.simulation_rate = fdm.get_delta_t()
 
-if args.planetfile:
+if args.planet:
     fdm.load_planet(args.planetfile, False)
 
 if args.property: