diff --git a/packages/artisan/src/workers/ffprobe.ts b/packages/artisan/src/workers/ffprobe.ts
index 9ba79a00..20519485 100644
--- a/packages/artisan/src/workers/ffprobe.ts
+++ b/packages/artisan/src/workers/ffprobe.ts
@@ -34,8 +34,14 @@ export const ffprobeCallback: WorkerCallback<
       const stream = info.streams.find(
         (stream) => stream.codec_type === "audio",
       );
+
+      let language = info.format.tags?.["language"];
+      if (!language || typeof language === "number") {
+        language = undefined;
+      }
+
       result.audio[input.path] = {
-        language: info.format.tags?.["language"] as string,
+        language,
         channels: stream?.channels,
       };
     }
diff --git a/packages/artisan/src/workers/transcode.ts b/packages/artisan/src/workers/transcode.ts
index 8edf0674..cbdd648f 100644
--- a/packages/artisan/src/workers/transcode.ts
+++ b/packages/artisan/src/workers/transcode.ts
@@ -323,8 +323,8 @@ export function mergeInput(
     const info = probeResult.audio[partial.path];
     assert(info);
 
-    const language = partial.language ?? getLangCode(info.language);
-    assert(language, defaultReason("audio", "language"));
+    // Get the language code, if not found, we fallback to undecided.
+    const language = partial.language ?? getLangCode(info.language) ?? "und";
 
     // Assume when no channel metadata is found, we'll fallback to 2.
     const channels = partial.channels ?? info.channels ?? 2;