1 files changed, 3 insertions, 2 deletions
diff --git a/ext/fetch/26_fetch.js b/ext/fetch/26_fetch.js
index 2d7180691..edd14abf1 100644
--- a/ext/fetch/26_fetch.js
+++ b/ext/fetch/26_fetch.js
@@ -503,9 +503,10 @@
         // The spec is ambiguous here, see
         // https://github.com/WebAssembly/spec/issues/1138. The WPT tests
         // expect the raw value of the Content-Type attribute lowercased.
+        const contentType = res.headers.get("Content-Type");
         if (
-          StringPrototypeToLowerCase(res.headers.get("Content-Type")) !==
-            "application/wasm"
+          typeof contentType !== "string" ||
+          StringPrototypeToLowerCase(contentType) !== "application/wasm"
         ) {
           throw new TypeError("Invalid WebAssembly content type.");
         }