Laravel route with parameter causes 404

I have a route setup which is throwing a 404 in my Laravel 5.6 app.

The problematic route is:

Route::get('/project/{project_id}/issue/create', 'IssueController@create');

If I remove the {project_id} parameter the view loads..but I need to be able to pass this id since I will be using it on this view to create new issues that are assigned to a project. All of the other routes work without issue.

My routes file (web.php) looks like this:

Route::get('/projects', 'ProjectController@index');
Route::get('/project/{project_id}', 'ProjectController@show');
Route::get('/project/{project_id}/issue/{issue_id}', 'IssueController@show');
Route::get('/project/{project_id}/issue/create', 'IssueController@create');

And my create function in the IssueController file is this:

public function create()
{
    return view('issue.create');
}

via Chebli Mohamed