diff --git a/src/nav2_turtlebot_simulator/launch/simulator.launch.py b/src/nav2_turtlebot_simulator/launch/simulator.launch.py
index 480ea60..7c9bf3a 100644
--- a/src/nav2_turtlebot_simulator/launch/simulator.launch.py
+++ b/src/nav2_turtlebot_simulator/launch/simulator.launch.py
@@ -203,6 +203,23 @@ def create_mkmini_world(gazebo_dir):
             continue
         pose.text = ' '.join(values)
 
+    # The black wall is centered at the origin, so its pose is unaffected by
+    # the spacing expansion. Enlarge both its visual and collision mesh to
+    # retain the same relationship with the widened green obstacles.
+    for mesh in model.findall('.//mesh'):
+        if not (mesh.findtext('uri', default='').endswith('/wall.dae')):
+            continue
+        scale = mesh.find('scale')
+        if scale is None:
+            continue
+        values = scale.text.split()
+        if len(values) != 3:
+            continue
+        try:
+            scale.text = ' '.join(str(float(value) * MKMINI_WORLD_SPACING_SCALE) for value in values)
+        except ValueError:
+            continue
+
     model_tree.write(
         os.path.join(model_dir, 'model.sdf'),
         encoding='utf-8',