diff --git a/src/components/tree/tree.tsx b/src/components/tree/tree.tsx
index 2ed13a603..b1e9f52ca 100644
--- a/src/components/tree/tree.tsx
+++ b/src/components/tree/tree.tsx
@@ -68,12 +68,12 @@ export interface TreeComponentStateProps {
 }
 
 export interface TreeComponentState {
-  hoveredNode: {
+  hoveredNode?: {
     node: PhyloNode
     isBranch: boolean
   } | null
-  tree: PhyloTreeType | null
-  treeToo: PhyloTreeType | null
+  tree?: PhyloTreeType | null
+  treeToo?: PhyloTreeType | null
   geneSortFn?: (a: number, b: number) => number | (() => 0)
 }