diff --git a/plugins/3MFReader/ThreeMFWorkspaceReader.py b/plugins/3MFReader/ThreeMFWorkspaceReader.py
index 9ec711697e..daa49e5f95 100644
--- a/plugins/3MFReader/ThreeMFWorkspaceReader.py
+++ b/plugins/3MFReader/ThreeMFWorkspaceReader.py
@@ -33,12 +33,14 @@ class ThreeMFWorkspaceReader(WorkspaceReader):
         self._dialog = WorkspaceDialog()
         self._3mf_mesh_reader = None
         self._container_registry = ContainerRegistry.getInstance()
-        self._definition_container_suffix = ContainerRegistry.getMimeTypeForContainer(DefinitionContainer).preferredSuffix
+
+        # suffixes registered with the MineTypes don't start with a dot '.'
+        self._definition_container_suffix = "." + ContainerRegistry.getMimeTypeForContainer(DefinitionContainer).preferredSuffix
         self._material_container_suffix = None # We have to wait until all other plugins are loaded before we can set it
-        self._instance_container_suffix = ContainerRegistry.getMimeTypeForContainer(InstanceContainer).preferredSuffix
-        self._container_stack_suffix = ContainerRegistry.getMimeTypeForContainer(ContainerStack).preferredSuffix
-        self._extruder_stack_suffix = ContainerRegistry.getMimeTypeForContainer(ExtruderStack).preferredSuffix
-        self._global_stack_suffix = ContainerRegistry.getMimeTypeForContainer(GlobalStack).preferredSuffix
+        self._instance_container_suffix = "." + ContainerRegistry.getMimeTypeForContainer(InstanceContainer).preferredSuffix
+        self._container_stack_suffix = "." + ContainerRegistry.getMimeTypeForContainer(ContainerStack).preferredSuffix
+        self._extruder_stack_suffix = "." + ContainerRegistry.getMimeTypeForContainer(ExtruderStack).preferredSuffix
+        self._global_stack_suffix = "." + ContainerRegistry.getMimeTypeForContainer(GlobalStack).preferredSuffix
 
         self._resolve_strategies = {}