diff --git a/cura/Machines/VariantNode.py b/cura/Machines/VariantNode.py
index 334a01158b..b93be9773e 100644
--- a/cura/Machines/VariantNode.py
+++ b/cura/Machines/VariantNode.py
@@ -83,7 +83,7 @@ class VariantNode(ContainerNode):
     #   if there is no match.
     def preferredMaterial(self, approximate_diameter: int) -> MaterialNode:
         for base_material, material_node in self.materials.items():
-            if self.machine.preferred_material in base_material and approximate_diameter == int(material_node.getMetaDataEntry("approximate_diameter")):
+            if self.machine.preferred_material == base_material and approximate_diameter == int(material_node.getMetaDataEntry("approximate_diameter")):
                 return material_node
         # First fallback: Choose any material with matching diameter.
         for material_node in self.materials.values():