Change

app/controllers/pull_requests_controller.rb

@@ -70,7 +70,11 @@ class PullRequestsController < ApplicationController
             if local_requests.save
               remote_pr_params = @local_params
               remote_pr_params = remote_pr_params.merge(head: "#{params[:merge_user_login]}:#{params[:head]}").compact if local_requests.is_original && params[:merge_user_login]
-              gitea_request = Gitea::PullRequest::CreateService.call(current_user.try(:gitea_token), @project.owner, @repository.try(:identifier), remote_pr_params.except(:milestone))
+              if @project.forked_from_project_id.present?
+                gitea_request = Gitea::PullRequest::CreateService.call(current_user.try(:gitea_token), @project.fork_project.owner, @repository.try(:identifier), remote_pr_params.except(:milestone))
+              else
+                gitea_request = Gitea::PullRequest::CreateService.call(current_user.try(:gitea_token), @project.owner, @repository.try(:identifier), remote_pr_params.except(:milestone))
+              end
               if gitea_request && local_requests.update_attributes(gpid: gitea_request["number"])
                 if params[:issue_tag_ids].present?
                   params[:issue_tag_ids].each do |tag|