diff --git a/js/os.ts b/js/os.ts
index 33395b74dad995..f9b2beea94b257 100644
--- a/js/os.ts
+++ b/js/os.ts
@@ -52,13 +52,14 @@ export function codeFetch(
   const sourceCode = codeFetchRes.sourceCodeArray() || undefined;
   const outputCode = codeFetchRes.outputCodeArray() || undefined;
   const sourceMap = codeFetchRes.sourceMapArray() || undefined;
+  const decoder = new TextDecoder();
   return {
     moduleName: codeFetchRes.moduleName() || undefined,
     filename: codeFetchRes.filename() || undefined,
     mediaType: codeFetchRes.mediaType(),
-    sourceCode: sourceCode && new TextDecoder().decode(sourceCode),
-    outputCode: outputCode && new TextDecoder().decode(outputCode),
-    sourceMap: sourceMap && new TextDecoder().decode(sourceMap)
+    sourceCode: sourceCode && decoder.decode(sourceCode),
+    outputCode: outputCode && decoder.decode(outputCode),
+    sourceMap: sourceMap && decoder.decode(sourceMap)
   };
 }