diff --git a/static-serve-macro/src/lib.rs b/static-serve-macro/src/lib.rs
index 6808b3b..77b088a 100644
--- a/static-serve-macro/src/lib.rs
+++ b/static-serve-macro/src/lib.rs
@@ -790,11 +790,13 @@ fn maybe_get_compressed(compressed: &[u8], contents: &[u8]) -> Option<LitByteStr
 /// We accept the first guess because [`mime_guess` updates the order
 /// according to the latest IETF RTC](https://docs.rs/mime_guess/2.0.5/mime_guess/struct.MimeGuess.html#note-ordering)
 fn file_content_type(path: &Path, allow_unknown_extensions: bool) -> Result<String, error::Error> {
-    let ext = path.extension().ok_or(if allow_unknown_extensions {
-        return Ok(mime_guess::mime::APPLICATION_OCTET_STREAM.to_string());
-    } else {
-        error::Error::UnknownFileExtension(None)
-    })?;
+    let Some(ext) = path.extension() else {
+        return if allow_unknown_extensions {
+            Ok(mime_guess::mime::APPLICATION_OCTET_STREAM.to_string())
+        } else {
+            Err(error::Error::UnknownFileExtension(None))
+        };
+    };
 
     let ext = ext
         .to_str()
diff --git a/static-serve/tests/tests.rs b/static-serve/tests/tests.rs
index d40d3b9..13e9a4f 100644
--- a/static-serve/tests/tests.rs
+++ b/static-serve/tests/tests.rs
@@ -1369,3 +1369,24 @@ async fn serves_unknown_extensions() {
         .to_vec();
     assert_eq!(&collected_body_bytes, &b"example.wtf");
 }
+
+#[tokio::test]
+async fn allow_unknown_extensions_must_retain_content_type_for_known_extensions() {
+    // Given a router embedding assets with `allow_unknown_extensions = true` and a file with known
+    // extensions (in this case, `app.js`)
+    embed_assets!(
+        "../static-serve/test_assets/small",
+        allow_unknown_extensions = true
+    );
+    let router: Router<()> = static_router();
+
+    // When requesting `.app.js` from the router
+    let request = create_request("/app.js", &Compression::None);
+    let response = get_response(router.clone(), request).await;
+
+    // Then the content type must be `application/javascript`
+    assert_eq!(
+        "text/javascript",
+        response.headers().get("content-type").unwrap()
+    );
+}