diff --git a/impit-python/src/request.rs b/impit-python/src/request.rs
index 0a67909c..1e919f3b 100644
--- a/impit-python/src/request.rs
+++ b/impit-python/src/request.rs
@@ -137,10 +137,16 @@ pub(crate) fn to_body(
         None => ImpitBody::Empty,
         Some(RequestBody::Bytes(bytes)) => bytes.into(),
         Some(RequestBody::Form(form)) => {
-            headers.get_or_insert_default().insert(
-                "Content-Type".to_string(),
-                "application/x-www-form-urlencoded".to_string(),
-            );
+            let headers = headers.get_or_insert_default();
+            if !headers
+                .keys()
+                .any(|name| name.eq_ignore_ascii_case("content-type"))
+            {
+                headers.insert(
+                    "Content-Type".to_string(),
+                    "application/x-www-form-urlencoded".to_string(),
+                );
+            }
             form_to_bytes(form).into()
         }
         Some(RequestBody::Text(text)) => text.into_bytes().into(),
diff --git a/impit-python/test/async_client_test.py b/impit-python/test/async_client_test.py
index 459fd8df..13b2308e 100644
--- a/impit-python/test/async_client_test.py
+++ b/impit-python/test/async_client_test.py
@@ -610,6 +610,21 @@ async def test_form_non_ascii(self, browser: Browser) -> None:
         assert response.status_code == 200
         assert json.loads(response.text)['form']['Impit-Test'] == '👾🕵🏻‍♂️🧑‍💻'
 
+    @pytest.mark.asyncio
+    async def test_form_keeps_custom_content_type(self, browser: Browser) -> None:
+        impit = AsyncClient(browser=browser)
+
+        with echoing_server() as port:
+            response = await impit.post(
+                f'http://localhost:{port}/',
+                data={'Impit-Test': 'foo'},
+                headers={'Content-Type': 'application/x-www-form-urlencoded; charset=utf-8'},
+                timeout=5,
+            )
+
+        assert 'content-type: application/x-www-form-urlencoded; charset=utf-8\r\n' in response.text.lower()
+        assert response.text.endswith('Impit-Test=foo')
+
     @pytest.mark.asyncio
     async def test_passing_binary_body(self, browser: Browser) -> None:
         impit = AsyncClient(browser=browser)
diff --git a/impit-python/test/basic_client_test.py b/impit-python/test/basic_client_test.py
index 795981ec..b1a6de01 100644
--- a/impit-python/test/basic_client_test.py
+++ b/impit-python/test/basic_client_test.py
@@ -524,6 +524,20 @@ def test_form_non_ascii(self, browser: Browser) -> None:
         assert response.status_code == 200
         assert response.json()['form']['Impit-Test'] == '👾🕵🏻‍♂️🧑‍💻'
 
+    def test_form_keeps_custom_content_type(self, browser: Browser) -> None:
+        impit = Client(browser=browser)
+
+        with echoing_server() as port:
+            response = impit.post(
+                f'http://localhost:{port}/',
+                data={'Impit-Test': 'foo'},
+                headers={'Content-Type': 'application/x-www-form-urlencoded; charset=utf-8'},
+                timeout=5,
+            )
+
+        assert 'content-type: application/x-www-form-urlencoded; charset=utf-8\r\n' in response.text.lower()
+        assert response.text.endswith('Impit-Test=foo')
+
     def test_passing_binary_body(self, browser: Browser) -> None:
         impit = Client(browser=browser)