diff --git a/.changeset/true-bees-sniff.md b/.changeset/true-bees-sniff.md
new file mode 100644
index 00000000..df4e6846
--- /dev/null
+++ b/.changeset/true-bees-sniff.md
@@ -0,0 +1,5 @@
+---
+"@browserbasehq/stagehand": patch
+---
+
+handle namespaced elements in xpath build step
diff --git a/evals/evals.config.json b/evals/evals.config.json
index 06ed6459..9d3c7ccb 100644
--- a/evals/evals.config.json
+++ b/evals/evals.config.json
@@ -418,6 +418,10 @@
     {
       "name": "agent/sign_in",
       "categories": ["agent"]
+    },
+    {
+      "name": "namespace_xpath",
+      "categories": ["act"]
     }
   ]
 }
diff --git a/evals/tasks/namespace_xpath.ts b/evals/tasks/namespace_xpath.ts
new file mode 100644
index 00000000..fe12f500
--- /dev/null
+++ b/evals/tasks/namespace_xpath.ts
@@ -0,0 +1,39 @@
+import { EvalFunction } from "@/types/evals";
+
+export const namespace_xpath: EvalFunction = async ({
+  debugUrl,
+  sessionUrl,
+  stagehand,
+  logger,
+}) => {
+  try {
+    await stagehand.page.goto(
+      "https://browserbase.github.io/stagehand-eval-sites/sites/namespaced-xpath/",
+    );
+
+    await stagehand.page.act({
+      action: "fill 'nunya' into the 'type here' form",
+    });
+
+    const inputValue = await stagehand.page.locator("#ns-text").inputValue();
+    // confirm that the form was filled
+    const formHasBeenFilled = inputValue === "nunya";
+
+    return {
+      _success: formHasBeenFilled,
+      debugUrl,
+      sessionUrl,
+      logs: logger.getLogs(),
+    };
+  } catch (error) {
+    return {
+      _success: false,
+      error: error,
+      debugUrl,
+      sessionUrl,
+      logs: logger.getLogs(),
+    };
+  } finally {
+    await stagehand.close();
+  }
+};
diff --git a/lib/a11y/utils.ts b/lib/a11y/utils.ts
index e603961b..6c77af94 100644
--- a/lib/a11y/utils.ts
+++ b/lib/a11y/utils.ts
@@ -222,13 +222,18 @@ export async function buildBackendIdMaps(
           const tag = lc(String(child.nodeName));
           const key = `${child.nodeType}:${tag}`;
           const idx = (ctr[key] = (ctr[key] ?? 0) + 1);
-          segs.push(
-            child.nodeType === 3
-              ? `text()[${idx}]`
-              : child.nodeType === 8
-                ? `comment()[${idx}]`
+          if (child.nodeType === 3) {
+            segs.push(`text()[${idx}]`);
+          } else if (child.nodeType === 8) {
+            segs.push(`comment()[${idx}]`);
+          } else {
+            // Element node: if qualified (e.g. "as:ajaxinclude"), switch to name()='as:ajaxinclude'
+            segs.push(
+              tag.includes(":")
+                ? `*[name()='${tag}'][${idx}]`
                 : `${tag}[${idx}]`,
-          );
+            );
+          }
         }
         // push R→L so traversal remains L→R
         for (let i = kids.length - 1; i >= 0; i--) {