diff --git a/static/main.css b/static/main.css
index 1cdf037..e151d54 100644
--- a/static/main.css
+++ b/static/main.css
@@ -1459,9 +1459,8 @@ body {
   background-color: rgb(0 0 0 / var(--tw-bg-opacity));
 }
 
-.bg-white {
-  --tw-bg-opacity: 1;
-  background-color: rgb(255 255 255 / var(--tw-bg-opacity));
+.bg-inherit {
+  background-color: inherit;
 }
 
 .bg-white\/50 {
diff --git a/templates/partials/header.html b/templates/partials/header.html
index 2ee18a4..84524dc 100644
--- a/templates/partials/header.html
+++ b/templates/partials/header.html
@@ -34,7 +34,13 @@
 
       // dark theme
       const setDark = (isDark) => {
-        htmlClass[isDark ? "add" : "remove"]("dark");
+        if (isDark) {
+          document.body.dispatchEvent(new CustomEvent("set-theme", { detail: "dark" }));
+          htmlClass.add("dark");
+        } else {
+          document.body.dispatchEvent(new CustomEvent("set-theme", { detail: "light" }));
+          htmlClass.remove("dark");
+        }
         localStorage.setItem("dark", isDark);
       };
 
diff --git a/templates/partials/mermaid.html b/templates/partials/mermaid.html
index a80863e..7065da2 100644
--- a/templates/partials/mermaid.html
+++ b/templates/partials/mermaid.html
@@ -1,4 +1,32 @@
 <script type="module">
   import mermaid from "https://cdn.jsdelivr.net/npm/mermaid@10/dist/mermaid.esm.min.mjs";
-  mermaid.initialize({ startOnLoad: true });
+
+  const initMermaid = (isDark) => {
+    mermaid.initialize({
+      theme: isDark ? "dark" : "default",
+      startOnLoad: false,
+    });
+    mermaid.run();
+  };
+
+  // Add data-mermaid-code attribute on all mermaid block.
+  document.querySelectorAll(".mermaid").forEach((element) => {
+    element.setAttribute("data-mermaid-code", element.innerHTML);
+  });
+
+  // Re-render mermaid when theme changed.
+  document.body.addEventListener("set-theme", (e) => {
+    document.querySelectorAll(".mermaid").forEach((element) => {
+      const mermaidCode = element.getAttribute("data-mermaid-code");
+      if (mermaidCode != null) {
+        element.removeAttribute("data-processed");
+        element.innerHTML = mermaidCode;
+      }
+    });
+    initMermaid(e.detail == "dark");
+  });
+
+  // The es module script will load defer, so the localStorage should already be set by script in header.
+  // If this script is loaded first, the script in header will dispatch an event to re-render mermaid, it's works too.
+  initMermaid(localStorage.getItem("dark") === "true");
 </script>
diff --git a/templates/shortcodes/mermaid.html b/templates/shortcodes/mermaid.html
index d53ecc6..d94eb1a 100644
--- a/templates/shortcodes/mermaid.html
+++ b/templates/shortcodes/mermaid.html
@@ -1,3 +1,3 @@
-<pre class="mermaid bg-white">
+<pre class="mermaid bg-inherit">
   {{ body | trim_start_matches(pat="```mermaid") | trim_start_matches(pat="```") | trim_end_matches(pat="```") }}
 </pre>