diff --git a/tut_mission_B737.py b/tut_mission_B737.py
index 89ea5fa..23a46c3 100644
--- a/tut_mission_B737.py
+++ b/tut_mission_B737.py
@@ -295,7 +295,7 @@ def vehicle_setup():
     wing.tag = 'vertical_stabilizer'    
 
     wing.aspect_ratio            = 1.91
-    wing.sweep.quarter_chord     = 25. * Units.deg
+    wing.sweeps.quarter_chord     = 25. * Units.deg
     wing.thickness_to_chord      = 0.08
     wing.taper                   = 0.25
     wing.span_efficiency         = 0.9