diff --git a/routers/private/hook_pre_receive.go b/routers/private/hook_pre_receive.go
index 8c2c97590f..41bd1f2931 100644
--- a/routers/private/hook_pre_receive.go
+++ b/routers/private/hook_pre_receive.go
@@ -4,6 +4,7 @@
 package private
 
 import (
+	"errors"
 	"fmt"
 	"net/http"
 	"os"
@@ -472,24 +473,27 @@ func preReceiveFor(ctx *preReceiveContext, refFullName git.RefName) {
 	}
 }
 
-func canUpdateAgitPull(ctx *preReceiveContext, pull *issues_model.PullRequest) bool {
+func canUpdateAgitPull(ctx *preReceiveContext, pull *issues_model.PullRequest) error {
 	if pull.Flow != issues_model.PullRequestFlowAGit {
-		return false
+		return errors.New("Pull request that are not created through agit cannot be updated using agit")
 	}
 
 	if ctx.opts.UserID == pull.Issue.PosterID {
-		return true
+		return nil
 	}
 
 	if !pull.AllowMaintainerEdit {
-		return false
+		return fmt.Errorf("The author does not allow maintainers to edit this pull request")
 	}
 
 	if !ctx.loadPusherAndPermission() {
-		return false
+		return fmt.Errorf("Internal Server Error (no specific error)")
 	}
 
-	return ctx.userPerm.CanWrite(unit.TypeCode)
+	if ctx.userPerm.CanWrite(unit.TypeCode) {
+		return errors.New("You have no permission to update this pull request")
+	}
+	return nil
 }
 
 func preReceiveForReview(ctx *preReceiveContext, refFullName git.RefName) {
@@ -535,9 +539,9 @@ func preReceiveForReview(ctx *preReceiveContext, refFullName git.RefName) {
 		return
 	}
 
-	if !canUpdateAgitPull(ctx, pull) {
+	if err := canUpdateAgitPull(ctx, pull); err != nil {
 		ctx.JSON(http.StatusForbidden, private.Response{
-			UserMsg: "Unknow pull request.",
+			UserMsg: err.Error(),
 		})
 		return
 	}
diff --git a/services/agit/agit.go b/services/agit/agit.go
index dcfb2ea6a2..9f6d85d5e4 100644
--- a/services/agit/agit.go
+++ b/services/agit/agit.go
@@ -137,6 +137,7 @@ func ProcReceive(ctx context.Context, repo *repo_model.Repository, gitRepo *git.
 				})
 				continue
 			}
+			log.Trace("Pull request index: %d", pullIndex)
 			pull, err := issues_model.GetPullRequestByIndex(ctx, repo.ID, pullIndex)
 			if err != nil {
 				results = append(results, private.HookProcReceiveRefResult{