diff --git a/src/pyrobusta/protocol/http.py b/src/pyrobusta/protocol/http.py
index 93d55ab..ccf4e2b 100644
--- a/src/pyrobusta/protocol/http.py
+++ b/src/pyrobusta/protocol/http.py
@@ -94,30 +94,6 @@ class HttpEngine:
         505,
         b"505 Version Not Supported",
     )
-    CONTENT_TYPES = (
-        b"raw",
-        b"application/octet-stream",
-        b"html",
-        b"text/html",
-        b"css",
-        b"text/css",
-        b"js",
-        b"application/javascript",
-        b"json",
-        b"application/json",
-        b"ico",
-        b"image/x-icon",
-        b"jpeg",
-        b"image/jpeg",
-        b"jpg",
-        b"image/jpeg",
-        b"png",
-        b"image/png",
-        b"txt",
-        b"text/plain",
-        b"gif",
-        b"image/gif",
-    )
 
     DELETE = b"DELETE"
     GET = b"GET"
@@ -319,7 +295,10 @@ def _parse_headers(cls, raw_headers: memoryview) -> dict[str, str | int]:
                 value = int(value.strip())
             else:
                 value = value.strip().decode("ascii")
-            headers[name] = value
+            if name not in headers and value:
+                headers[name] = value
+            elif value:
+                headers[name] += ", " + value  # Combined field value
         return headers
 
     @staticmethod
@@ -412,7 +391,7 @@ def write_response_head(self, tx):
     def set_response_body(
         self,
         body: bytes | str | dict | tuple | list,
-        content_type: bytes = b"text/plain",
+        content_type: str = "text/plain",
     ):
         """
         Serialize and wrap the response body with a BytesIO
@@ -436,7 +415,7 @@ def set_response_body(
         self.set_response_header(
             b"content-length", str(len(body_encoded)).encode("ascii")
         )
-        self.set_response_header(b"content-type", content_type)
+        self.set_response_header(b"content-type", content_type.encode("ascii"))
         if self.method != self.HEAD:
             self.resp_handler = BytesIO(body_encoded)
 
@@ -702,7 +681,6 @@ def _app_endpoint_st(self, rx):
                 dtype, data = callback(
                     self, bytes(rx.peek(self.headers["content-length"]))
                 )
-            dtype = dtype.encode("ascii")
         else:
             if not callable(callback):
                 # Handle as a file path
@@ -711,10 +689,8 @@ def _app_endpoint_st(self, rx):
                 )
                 return
             dtype, data = callback(self, b"")
-            dtype = dtype.encode("ascii")
-        self.set_response_header(b"content-type", dtype)
 
-        if dtype.startswith(b"multipart/"):
+        if dtype.startswith("multipart/"):
             self.state = lambda _rx: self._generate_multipart_response(_rx, data, dtype)
             return
 
diff --git a/src/pyrobusta/protocol/http_file_server.py b/src/pyrobusta/protocol/http_file_server.py
index f128d37..a8c278b 100644
--- a/src/pyrobusta/protocol/http_file_server.py
+++ b/src/pyrobusta/protocol/http_file_server.py
@@ -9,6 +9,31 @@
 from pyrobusta.protocol import http
 from pyrobusta.utils.helpers import normalize_path, add_method
 
+CONTENT_TYPES = (
+    b"raw",
+    b"application/octet-stream",
+    b"html",
+    b"text/html",
+    b"css",
+    b"text/css",
+    b"js",
+    b"application/javascript",
+    b"json",
+    b"application/json",
+    b"ico",
+    b"image/x-icon",
+    b"jpeg",
+    b"image/jpeg",
+    b"jpg",
+    b"image/jpeg",
+    b"png",
+    b"image/png",
+    b"txt",
+    b"text/plain",
+    b"gif",
+    b"image/gif",
+)
+
 
 def _send_file_st(self, _, file_path: bytes):
     """
@@ -38,9 +63,9 @@ def _send_file_st(self, _, file_path: bytes):
             self.terminate(404, True)
             return
     try:
-        content_type = self._lookup(self.CONTENT_TYPES, extension)
+        content_type = self._lookup(CONTENT_TYPES, extension)
     except ValueError:
-        content_type = self._lookup(self.CONTENT_TYPES, b"raw")
+        content_type = self._lookup(CONTENT_TYPES, b"raw")
     try:
         self.set_response_header(
             b"content-length", str(stat(norm_path)[6]).encode("ascii")
diff --git a/src/pyrobusta/protocol/http_multipart.py b/src/pyrobusta/protocol/http_multipart.py
index fbc0862..7e8cb5d 100644
--- a/src/pyrobusta/protocol/http_multipart.py
+++ b/src/pyrobusta/protocol/http_multipart.py
@@ -8,7 +8,7 @@
 from pyrobusta.utils.helpers import add_method
 
 
-def _generate_multipart_response(self, _, callback: callable, dtype: bytes):
+def _generate_multipart_response(self, _, callback: callable, dtype: str):
     """
     Generate multipart response depening on the exact content type.
     The callback function is called without arguments, and it must return bytes-like objects.
@@ -19,7 +19,9 @@ def _generate_multipart_response(self, _, callback: callable, dtype: bytes):
         raise ValueError("Invalid response handler")
     self.terminate(200, True)
     boundary = self.MULTIPART_BOUNDARY
-    self.set_response_header(b"content-type", dtype + b"; boundary=" + boundary)
+    self.set_response_header(
+        b"content-type", dtype.encode("ascii") + b"; boundary=" + boundary
+    )
     if self.method != self.HEAD:
         self.resp_handler = self._multipart_wrapper_factory(callback, boundary)
 
@@ -135,9 +137,8 @@ def _parse_complete_part_st(self, rx):
         raise http.InvalidContentLength()
     self.mp_is_last = True
     dtype, data = callback(self, (part_headers, part_body))
-    self.set_response_header(b"content-type", dtype.encode("ascii"))
     self.terminate(200, True)
-    self.set_response_body(data)
+    self.set_response_body(data, dtype)
 
 
 def apply_patches():
diff --git a/tests/unit/test_http.py b/tests/unit/test_http.py
index 949bc2f..96be22d 100644
--- a/tests/unit/test_http.py
+++ b/tests/unit/test_http.py
@@ -170,6 +170,19 @@ def test_header_parsing_error(self):
             with self.assertRaises(self.http_module.InvalidHeaders):
                 self.engine._parse_headers(case)
 
+    def test_header_parsing_combined(self):
+        for case in (
+            (
+                b"field-name: value1\r\nfield-name: value2",
+                {"field-name": "value1, value2"},
+            ),
+            (
+                b"field-name: \r\nfield-name: value1\r\nfield-name:\r\nfield-name: value2",
+                {"field-name": "value1, value2"},
+            ),
+        ):
+            self.assertEqual(self.engine._parse_headers(case[0]), case[1])
+
     def test_routing_unsupported_method(self):
         self.engine.state = self.engine._route_request_st
         self.engine.url = b"/api/test"