diff --git a/src/bonsai/bonsai/bim/module/model/slab.py b/src/bonsai/bonsai/bim/module/model/slab.py
index 7630ef258c..3dcbf2aef0 100644
--- a/src/bonsai/bonsai/bim/module/model/slab.py
+++ b/src/bonsai/bonsai/bim/module/model/slab.py
@@ -249,6 +249,7 @@ class DumbSlabPlaner:
         self.change_thickness(element, total_thickness)
 
     def change_thickness(self, element: ifcopenshell.entity_instance, thickness: float) -> None:
+        self.unit_scale = ifcopenshell.util.unit.calculate_unit_scale(tool.Ifc.get())
         if tool.Model.get_usage_type(element) != "LAYER3":
             return
         layer_params = tool.Model.get_material_layer_parameters(element)
diff --git a/src/bonsai/test/bim/feature/type.feature b/src/bonsai/test/bim/feature/type.feature
index 1efefef446..9bae601b30 100644
--- a/src/bonsai/test/bim/feature/type.feature
+++ b/src/bonsai/test/bim/feature/type.feature
@@ -110,7 +110,7 @@ Scenario: Assign type - assign to a type with a material layer set, which automa
     And the object "IfcWall/Unnamed" has a "100" thick layered material containing the material "Default"
     And the object "IfcWall/Unnamed" dimensions are ".5,.1,.5"
 
-Scenario: Assign type - assign to a different type with a material layer set
+Scenario: Assign type - assign to a different type with a LAYER2 material layer set
     Given an empty IFC project
     And I add a cube
     And the object "Cube" is selected
@@ -149,6 +149,23 @@ Scenario: Assign type - assign to a different type with a material layer set
     Then the object "IfcWall/Cube" has a "200" thick layered material containing the material "Default"
     And the object "IfcWall/Cube" dimensions are "1,.2,1"
 
+Scenario: Assign type - assign to a different type with a LAYER3 material layer set
+    Given an empty IFC project
+    And I load the demo construction library
+    And I set "scene.BIMModelProperties.ifc_class" to "IfcSlabType"
+    And the variable "element_type" is "[e for e in {ifc}.by_type('IfcSlabType') if e.Name == 'FLR200'][0].id()"
+    And I set "scene.BIMModelProperties.relating_type_id" to "{element_type}"
+    When I press "bim.add_occurrence"
+    Then the object "IfcSlab/Slab" is an "IfcSlab"
+    And the object "IfcSlab/Slab" dimensions are "1,1,0.2"
+    And the object "IfcSlab/Slab" bottom left corner is at "0,0,0"
+    And the object "IfcSlab/Slab" top right corner is at "1,1,0.2"
+    When I look at the "Type" panel
+    And I click "GREASEPENCIL"
+    And I set the "relating_type" property to "FLR300"
+    And I click "CHECKMARK"
+    Then the object "IfcSlab/Slab" dimensions are "1,1,0.3"
+
 Scenario: Assign type - assign to a type with a material profile set
     Given an empty IFC project
     And I add a cube