diff --git a/modules/repository/env.go b/modules/repository/env.go
index 78e06f86fb614..55a81f006e2bf 100644
--- a/modules/repository/env.go
+++ b/modules/repository/env.go
@@ -25,6 +25,7 @@ const (
 	EnvKeyID        = "GITEA_KEY_ID" // public key ID
 	EnvDeployKeyID  = "GITEA_DEPLOY_KEY_ID"
 	EnvPRID         = "GITEA_PR_ID"
+	EnvPRIndex      = "GITEA_PR_INDEX" // not used by Gitea at the moment, it is for custom git hooks
 	EnvPushTrigger  = "GITEA_PUSH_TRIGGER"
 	EnvIsInternal   = "GITEA_INTERNAL_PUSH"
 	EnvAppURL       = "GITEA_ROOT_URL"
@@ -50,11 +51,11 @@ func InternalPushingEnvironment(doer *user_model.User, repo *repo_model.Reposito
 
 // PushingEnvironment returns an os environment to allow hooks to work on push
 func PushingEnvironment(doer *user_model.User, repo *repo_model.Repository) []string {
-	return FullPushingEnvironment(doer, doer, repo, repo.Name, 0)
+	return FullPushingEnvironment(doer, doer, repo, repo.Name, 0, 0)
 }
 
 // FullPushingEnvironment returns an os environment to allow hooks to work on push
-func FullPushingEnvironment(author, committer *user_model.User, repo *repo_model.Repository, repoName string, prID int64) []string {
+func FullPushingEnvironment(author, committer *user_model.User, repo *repo_model.Repository, repoName string, prID, prIndex int64) []string {
 	isWiki := "false"
 	if strings.HasSuffix(repoName, ".wiki") {
 		isWiki = "true"
@@ -75,6 +76,7 @@ func FullPushingEnvironment(author, committer *user_model.User, repo *repo_model
 		EnvPusherID+"="+strconv.FormatInt(committer.ID, 10),
 		EnvRepoID+"="+strconv.FormatInt(repo.ID, 10),
 		EnvPRID+"="+strconv.FormatInt(prID, 10),
+		EnvPRIndex+"="+strconv.FormatInt(prIndex, 10),
 		EnvAppURL+"="+setting.AppURL,
 		"SSH_ORIGINAL_COMMAND=gitea-internal",
 	)
diff --git a/services/pull/merge.go b/services/pull/merge.go
index 9c7e09a227e1d..f5430546a3b4f 100644
--- a/services/pull/merge.go
+++ b/services/pull/merge.go
@@ -403,6 +403,7 @@ func doMergeAndPush(ctx context.Context, pr *issues_model.PullRequest, doer *use
 		pr.BaseRepo,
 		pr.BaseRepo.Name,
 		pr.ID,
+		pr.Index,
 	)
 
 	mergeCtx.env = append(mergeCtx.env, repo_module.EnvPushTrigger+"="+string(pushTrigger))
diff --git a/services/pull/update_rebase.go b/services/pull/update_rebase.go
index e6845f6b143b6..6a70c03467c91 100644
--- a/services/pull/update_rebase.go
+++ b/services/pull/update_rebase.go
@@ -80,6 +80,7 @@ func updateHeadByRebaseOnToBase(ctx context.Context, pr *issues_model.PullReques
 			pr.HeadRepo,
 			pr.HeadRepo.Name,
 			pr.ID,
+			pr.Index,
 		)).
 		WithDir(mergeCtx.tmpBasePath).
 		WithStdout(mergeCtx.outbuf).
diff --git a/services/wiki/wiki.go b/services/wiki/wiki.go
index 25f836dd5d819..a9dc7269829f3 100644
--- a/services/wiki/wiki.go
+++ b/services/wiki/wiki.go
@@ -223,6 +223,7 @@ func updateWikiPage(ctx context.Context, doer *user_model.User, repo *repo_model
 			repo,
 			repo.Name+".wiki",
 			0,
+			0,
 		),
 	}); err != nil {
 		log.Error("Push failed: %v", err)
@@ -341,6 +342,7 @@ func DeleteWikiPage(ctx context.Context, doer *user_model.User, repo *repo_model
 			repo,
 			repo.Name+".wiki",
 			0,
+			0,
 		),
 	}); err != nil {
 		if git.IsErrPushOutOfDate(err) || git.IsErrPushRejected(err) {