diff --git a/assets/js/theme.js b/assets/js/theme.js
index 62dfc9d3..9a816245 100644
--- a/assets/js/theme.js
+++ b/assets/js/theme.js
@@ -551,7 +551,7 @@ class FixIt {
   }
 
   initMermaid() {
-    if (!window.mermaid) {
+    if (!window.mermaid?.initialize) {
       return;
     }
     const themes = window.mermaid.themes ?? ['default', 'dark'];