diff --git a/packages/viewer/src/mathml.ts b/packages/viewer/src/mathml.ts
index a9195409d..8cf0a0693 100644
--- a/packages/viewer/src/mathml.ts
+++ b/packages/viewer/src/mathml.ts
@@ -77,7 +77,15 @@ export async function renderMathML(properties: Properties, root: HTMLElement): P
 
   decodeSafeMathML(root, properties.ignored_containers);
 
-  for (const mathElement of [...root.getElementsByTagName("math")]) {
+  // Fixed to get all possible math elements, including namespaced ones.
+  const allMathElements = [
+    ...root.getElementsByTagName("math"), // Standard <math>
+    ...root.getElementsByTagNameNS("*", "math"), // Any valid namespaced math
+    ...root.querySelectorAll("m\\:math"), // CSS: <m:math> (literal colon)
+    ...root.querySelectorAll("mml\\:math"), // CSS: <mml:math> (literal colon)
+  ];
+
+  for (const mathElement of allMathElements) {
     const mml = serializeHtmlToXml(mathElement.outerHTML);
     try {
       let imgSource;