diff --git a/tests/functional/docroot/with_headers.txt.sub.headers b/tests/functional/docroot/with_headers.txt.sub.headers
index 4826221f55c1e3..71494fccf10f2b 100644
--- a/tests/functional/docroot/with_headers.txt.sub.headers
+++ b/tests/functional/docroot/with_headers.txt.sub.headers
@@ -3,3 +3,4 @@ Another-Header: {{$id:uuid()}}
 Same-Value-Header: {{$id}}
 Double-Header: PA
 Double-Header: SS
+Content-Type: text/html
diff --git a/tests/functional/test_handlers.py b/tests/functional/test_handlers.py
index 5974b85566e51c..9189725cb25ecc 100644
--- a/tests/functional/test_handlers.py
+++ b/tests/functional/test_handlers.py
@@ -18,6 +18,7 @@ def test_GET(self):
     def test_headers(self):
         resp = self.request("/with_headers.txt")
         self.assertEqual(200, resp.getcode())
+        self.assertEqual("text/html", resp.info()["Content-Type"])
         self.assertEqual("PASS", resp.info()["Custom-Header"])
         # This will fail if it isn't a valid uuid
         uuid.UUID(resp.info()["Another-Header"])
diff --git a/wptserve/handlers.py b/wptserve/handlers.py
index 9f60fd0d722d79..c40321dfeabb4d 100644
--- a/wptserve/handlers.py
+++ b/wptserve/handlers.py
@@ -147,9 +147,12 @@ def __call__(self, request, response):
             raise HTTPException(404)
 
     def get_headers(self, request, path):
-        rv = self.default_headers(path)
-        rv.extend(self.load_headers(request, os.path.join(os.path.split(path)[0], "__dir__")))
-        rv.extend(self.load_headers(request, path))
+        rv = (self.load_headers(request, os.path.join(os.path.split(path)[0], "__dir__")) +
+              self.load_headers(request, path))
+
+        if not any(key.lower() == "content-type" for (key, _) in rv):
+            rv.insert(0, ("Content-Type", guess_content_type(path)))
+
         return rv
 
     def load_headers(self, request, path):
@@ -206,9 +209,6 @@ def get_range_data(self, f, byte_range):
         f.seek(byte_range.lower)
         return f.read(byte_range.upper - byte_range.lower)
 
-    def default_headers(self, path):
-        return [("Content-Type", guess_content_type(path))]
-
 
 file_handler = FileHandler()