diff --git a/src/sentry/integrations/api/endpoints/organization_code_mapping_details.py b/src/sentry/integrations/api/endpoints/organization_code_mapping_details.py
index 67770f09cfdc..a255031efc69 100644
--- a/src/sentry/integrations/api/endpoints/organization_code_mapping_details.py
+++ b/src/sentry/integrations/api/endpoints/organization_code_mapping_details.py
@@ -12,6 +12,7 @@
     OrganizationIntegrationsLoosePermission,
 )
 from sentry.api.serializers import serialize
+from sentry.api.serializers.rest_framework.base import camel_to_snake_case, convert_dict_key_case
 from sentry.integrations.models.repository_project_path_config import RepositoryProjectPathConfig
 from sentry.integrations.services.integration import integration_service
 
@@ -44,17 +45,18 @@ def convert_args(self, request: Request, organization_id_or_slug, config_id, *ar
                 id=config_id,
                 organization_integration_id__in=[oi.id for oi in ois],
             )
-        except RepositoryProjectPathConfig.DoesNotExist:
+            # Only set when the request wants to move the mapping to another project.
+            # Normalize keys the way the serializer does first, otherwise a snake_case
+            # `project_id` skips the access check below but still moves the mapping.
+            data = convert_dict_key_case(request.data, camel_to_snake_case)
+            if data.get("project_id"):
+                kwargs["new_project"] = self.get_project(kwargs["organization"], data["project_id"])
+        except (RepositoryProjectPathConfig.DoesNotExist, ValueError):
             raise Http404
 
-        if request.data.get("projectId"):
-            kwargs["new_project"] = super().get_project(
-                kwargs["organization"], request.data.get("projectId")
-            )
-
         return (args, kwargs)
 
-    def put(self, request: Request, config_id, organization, config, new_project) -> Response:
+    def put(self, request: Request, config_id, organization, config, new_project=None) -> Response:
         """
         Update a repository project path config
         ``````````````````
@@ -68,8 +70,10 @@ def put(self, request: Request, config_id, organization, config, new_project) ->
         :param string default_branch:
         :auth: required
         """
-        project = config.project_repository.project
-        if not request.access.has_projects_access([project, new_project]):
+        projects = [config.project_repository.project]
+        if new_project is not None:
+            projects.append(new_project)
+        if not request.access.has_projects_access(projects):
             return self.respond(status=status.HTTP_403_FORBIDDEN)
 
         try:
diff --git a/tests/sentry/integrations/api/endpoints/test_organization_code_mapping_details.py b/tests/sentry/integrations/api/endpoints/test_organization_code_mapping_details.py
index ed8dc00b2165..921b206fea4e 100644
--- a/tests/sentry/integrations/api/endpoints/test_organization_code_mapping_details.py
+++ b/tests/sentry/integrations/api/endpoints/test_organization_code_mapping_details.py
@@ -71,6 +71,9 @@ def test_non_project_member_permissions(self) -> None:
         non_member_om = self.create_member(organization=self.org, user=non_member)
         self.login_as(user=non_member)
 
+        response = self.client.put(self.url, {"sourceRoot": ""})
+        assert response.status_code == status.HTTP_403_FORBIDDEN
+
         response = self.make_put({"sourceRoot": "newRoot"})
         assert response.status_code == status.HTTP_403_FORBIDDEN
 
@@ -102,6 +105,40 @@ def test_basic_edit(self) -> None:
         assert resp.data["id"] == str(self.config.id)
         assert resp.data["sourceRoot"] == "newRoot"
 
+    def test_edit_rejects_missing_required_fields(self) -> None:
+        resp = self.client.put(self.url, {"sourceRoot": ""})
+
+        assert resp.status_code == status.HTTP_400_BAD_REQUEST
+        assert resp.data == {
+            "projectId": ["This field is required."],
+            "repositoryId": ["This field is required."],
+            "stackRoot": ["This field is required."],
+        }
+
+    def test_edit_snake_case_project_id_is_access_checked(self) -> None:
+        member = self.create_user()
+        self.create_member(
+            organization=self.org, user=member, has_global_access=False, teams=[self.team]
+        )
+        self.login_as(user=member)
+
+        # every key is snake_case so `projectId` never appears in the body, but the
+        # serializer still reads it as project_id and would move the mapping
+        resp = self.client.put(
+            self.url,
+            {
+                "repository_id": self.repo.id,
+                "project_id": self.project2.id,
+                "stack_root": "/stack/root",
+                "source_root": "/source/root",
+                "default_branch": "master",
+            },
+        )
+
+        assert resp.status_code == status.HTTP_403_FORBIDDEN
+        self.config.refresh_from_db()
+        assert self.config.project_repository.project_id == self.project.id
+
     def test_basic_edit_from_member_permissions(self) -> None:
         self.login_as(user=self.user2)
         resp = self.make_put({"sourceRoot": "newRoot"})