diff --git a/src/Data.Tuple.Containing.purs b/src/Data.Tuple.Containing.purs
index 6e9d632..8656926 100644
--- a/src/Data.Tuple.Containing.purs
+++ b/src/Data.Tuple.Containing.purs
@@ -8,7 +8,7 @@ import Data.Tuple.Nested (type (/\), (/\))
 -- | given a tuple of any size with at least 1 value
 -- | of type `a`, `extract` the first occurence of `a`
 -- | from the tuple
-class TupleContaining a tup where
+class TupleContaining @a tup where
   extract :: tup -> a
 
 instance TupleContaining a a where
diff --git a/src/HTTP/Header.purs b/src/HTTP/Header.purs
index 4f4a640..e1a662a 100644
--- a/src/HTTP/Header.purs
+++ b/src/HTTP/Header.purs
@@ -69,7 +69,7 @@ instance Monoid Headers where
   mempty = wrap $ Map.empty
 
 class IntoHeaders a where
-  headers :: forall m. MonadEffect m => a -> m Headers
+  headers :: a -> Effect Headers
 
 instance IntoHeaders Headers where
   headers = pure
diff --git a/src/HTTP/Request.purs b/src/HTTP/Request.purs
index d618d9c..974ed0f 100644
--- a/src/HTTP/Request.purs
+++ b/src/HTTP/Request.purs
@@ -84,7 +84,7 @@ bodyHeaders (BodyEmpty) = pure mempty
 bodyHeaders (BodyString _ ct) = liftEffect $ Header.headers ct
 bodyHeaders (BodyBuffer _ ct) = liftEffect $ Header.headers ct
 bodyHeaders (BodyArrayBuffer _ ct) = liftEffect $ Header.headers ct
-bodyHeaders (BodyBlob b) = Header.headers <<< map (ContentType <<< MIME.fromString <<< unwrap) $ Blob.type_ b
+bodyHeaders (BodyBlob b) = liftEffect $ Header.headers <<< map (ContentType <<< MIME.fromString <<< unwrap) $ Blob.type_ b
 
 bodyToRaw :: forall m. MonadAff m => Body -> m RawRequestBody
 bodyToRaw (BodyString body ct) = flip bind bodyToRaw $ liftEffect $ map (flip BodyBuffer ct) $ Buffer.fromString body UTF8
@@ -109,6 +109,20 @@ class Request a where
   requestHeaders :: forall m. MonadAff m => a -> m (Map String String)
 
 instance
+  ( TupleContaining Body a
+  , TupleContaining URL a
+  , TupleContaining Method a
+  , TupleContaining (Effect Headers) a
+  ) =>
+  Request a where
+  requestUrl = pure <<< extract
+  requestMethod = pure <<< extract
+  requestBody = map Just <<< bodyToRaw <<< extract
+  requestHeaders req = do
+    (Headers hs) <- liftEffect $ extract req
+    (Headers bodyHs) <- bodyHeaders $ extract req
+    pure $ Map.union hs bodyHs
+else instance
   ( TupleContaining Body a
   , TupleContaining URL a
   , TupleContaining Method a
@@ -142,6 +156,17 @@ else instance
   requestMethod = pure <<< extract
   requestBody _ = Just <$> bodyToRaw BodyEmpty
   requestHeaders = (\(Headers h) -> pure h) <<< extract
+else instance
+  ( MonadEffect m
+  , TupleContaining (Effect Headers) a
+  , TupleContaining URL a
+  , TupleContaining Method a
+  ) =>
+  Request a where
+  requestUrl = pure <<< extract
+  requestMethod = pure <<< extract
+  requestBody _ = Just <$> bodyToRaw BodyEmpty
+  requestHeaders = liftEffect <<< map (\(Headers h) -> h) <<< extract @(Effect Headers)
 else instance
   ( TupleContaining URL a
   , TupleContaining Method a