diff --git a/graph_node_renderer/variable_viewer.gd b/graph_node_renderer/variable_viewer.gd
index 2cf5148..4aa44a4 100644
--- a/graph_node_renderer/variable_viewer.gd
+++ b/graph_node_renderer/variable_viewer.gd
@@ -130,7 +130,14 @@ func add_item(item_name: String, item_value: Variant, parent: TreeItem = root, c
 	var item := variable_tree.create_item(parent)
 	item.set_text(0, item_name)
 
-	var type: DeckType.Types = DeckType.INVERSE_GODOT_TYPES_MAP[typeof(item_value)]
+	# TODO: proper null handling
+	var value_type := typeof(item_value)
+	var type: DeckType.Types
+	if value_type == TYPE_NIL:
+		type = DeckType.Types.STRING
+		item_value = "<nothing>"
+	else:
+		type = DeckType.INVERSE_GODOT_TYPES_MAP[typeof(item_value)]
 	item.set_meta(&"container", container)
 	item.set_meta(&"indexed", indexed)