diff --git a/ahb_techdraw_extensions.py b/ahb_techdraw_extensions.py
index 43dda58..5874fb8 100644
--- a/ahb_techdraw_extensions.py
+++ b/ahb_techdraw_extensions.py
@@ -521,14 +521,15 @@ class TechDrawExtensions:
 		obj = self.getBalloonSourcePart(balloon)
 		path = self.getBalloonSourcePartPath(balloon)
 		
-		partDisplayName = 'Inconnu' if obj is None else self.getPartDisplayName(obj)
+		if obj is not None:
+			objectCenterView = workbench.techDrawExtensions.computePartCenter(view, obj, path)
 		
-		objectCenterView = workbench.techDrawExtensions.computePartCenter(view, obj, path)
-		
-		balloon.OriginX = objectCenterView.x + balloon.Assembly_handbook_OriginOffsetX
-		balloon.OriginY = objectCenterView.y + balloon.Assembly_handbook_OriginOffsetY
+			balloon.OriginX = objectCenterView.x + balloon.Assembly_handbook_OriginOffsetX
+			balloon.OriginY = objectCenterView.y + balloon.Assembly_handbook_OriginOffsetY
+			
+			partDisplayName = 'Inconnu' if obj is None else self.getPartDisplayName(obj)
+			balloon.Text = partDisplayName
 		
-		balloon.Text = partDisplayName
 		balloon.ViewObject.Font = 'DejaVu Sans'
 		balloon.ViewObject.Fontsize = 4
 		balloon.BubbleShape = 'Inspection'