diff --git a/templates/repo/diff/box.tmpl b/templates/repo/diff/box.tmpl
index 1aac4acc2b0e4..64d9d82128653 100644
--- a/templates/repo/diff/box.tmpl
+++ b/templates/repo/diff/box.tmpl
@@ -21,7 +21,8 @@
 					{{svg "octicon-sidebar-expand" 20 "icon gt-hidden"}}
 				</button>
 				<script>
-					const diffTreeVisible = localStorage?.getItem('diff_file_tree_visible') === 'true';
+					// Default to true if unset
+					const diffTreeVisible = localStorage?.getItem('diff_file_tree_visible') !== 'false';
 					const diffTreeBtn = document.querySelector('.diff-toggle-file-tree-button');
 					const diffTreeIcon = `.octicon-sidebar-${diffTreeVisible ? 'expand' : 'collapse'}`;
 					diffTreeBtn.querySelector(diffTreeIcon).classList.remove('gt-hidden');
diff --git a/web_src/js/components/DiffFileTree.vue b/web_src/js/components/DiffFileTree.vue
index 734ad80e8bfae..c4d1c614de92a 100644
--- a/web_src/js/components/DiffFileTree.vue
+++ b/web_src/js/components/DiffFileTree.vue
@@ -89,7 +89,8 @@ export default {
     }
   },
   mounted() {
-    this.store.fileTreeIsVisible = localStorage.getItem(LOCAL_STORAGE_KEY) === 'true';
+    // Default to true if unset
+    this.store.fileTreeIsVisible = localStorage.getItem(LOCAL_STORAGE_KEY) !== 'false';
     document.querySelector('.diff-toggle-file-tree-button').addEventListener('click', this.toggleVisibility);
 
     this.hashChangeListener = () => {