diff --git a/routers/web/web.go b/routers/web/web.go
index 6b649dc1f5..98cdf8b964 100644
--- a/routers/web/web.go
+++ b/routers/web/web.go
@@ -1225,10 +1225,11 @@ func registerWebRoutes(m *web.Router) {
 	// end "/{username}/{reponame}": view milestone, label, issue, pull, etc
 
 	m.Group("/{username}/{reponame}/{type:issues}", func() {
+		// these handlers also check unit permissions internally
 		m.Get("", repo.Issues)
-		m.Get("/{index}", repo.ViewIssue)
-	}, optSignIn, context.RepoAssignment, context.RequireUnitReader(unit.TypeIssues, unit.TypeExternalTracker))
-	// end "/{username}/{reponame}": issue/pull list, issue/pull view, external tracker
+		m.Get("/{index}", repo.ViewIssue) // also do pull-request redirection (".../issues/{PR-number}" -> ".../pulls/{PR-number}")
+	}, optSignIn, context.RepoAssignment, context.RequireUnitReader(unit.TypeIssues, unit.TypePullRequests, unit.TypeExternalTracker))
+	// end "/{username}/{reponame}": issue list, issue view (pull-request redirection), external tracker
 
 	m.Group("/{username}/{reponame}", func() { // edit issues, pulls, labels, milestones, etc
 		m.Group("/issues", func() {
diff --git a/tests/integration/issue_test.go b/tests/integration/issue_test.go
index 3b5f1534ef..613353e55c 100644
--- a/tests/integration/issue_test.go
+++ b/tests/integration/issue_test.go
@@ -14,8 +14,10 @@ import (
 	"testing"
 	"time"
 
+	"code.gitea.io/gitea/models/db"
 	issues_model "code.gitea.io/gitea/models/issues"
 	repo_model "code.gitea.io/gitea/models/repo"
+	"code.gitea.io/gitea/models/unit"
 	"code.gitea.io/gitea/models/unittest"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/indexer/issues"
@@ -474,19 +476,38 @@ func TestIssueRedirect(t *testing.T) {
 	session := loginUser(t, "user2")
 
 	// Test external tracker where style not set (shall default numeric)
-	req := NewRequest(t, "GET", path.Join("org26", "repo_external_tracker", "issues", "1"))
+	req := NewRequest(t, "GET", "/org26/repo_external_tracker/issues/1")
 	resp := session.MakeRequest(t, req, http.StatusSeeOther)
 	assert.Equal(t, "https://tracker.com/org26/repo_external_tracker/issues/1", test.RedirectURL(resp))
 
 	// Test external tracker with numeric style
-	req = NewRequest(t, "GET", path.Join("org26", "repo_external_tracker_numeric", "issues", "1"))
+	req = NewRequest(t, "GET", "/org26/repo_external_tracker_numeric/issues/1")
 	resp = session.MakeRequest(t, req, http.StatusSeeOther)
 	assert.Equal(t, "https://tracker.com/org26/repo_external_tracker_numeric/issues/1", test.RedirectURL(resp))
 
 	// Test external tracker with alphanumeric style (for a pull request)
-	req = NewRequest(t, "GET", path.Join("org26", "repo_external_tracker_alpha", "issues", "1"))
+	req = NewRequest(t, "GET", "/org26/repo_external_tracker_alpha/issues/1")
 	resp = session.MakeRequest(t, req, http.StatusSeeOther)
-	assert.Equal(t, "/"+path.Join("org26", "repo_external_tracker_alpha", "pulls", "1"), test.RedirectURL(resp))
+	assert.Equal(t, "/org26/repo_external_tracker_alpha/pulls/1", test.RedirectURL(resp))
+
+	// test to check that the PR redirection works if the issue unit is disabled
+	// repo1 is a normal repository with issue unit enabled, visit issue 2(which is a pull request)
+	// will redirect to pulls
+	req = NewRequest(t, "GET", "/user2/repo1/issues/2")
+	resp = session.MakeRequest(t, req, http.StatusSeeOther)
+	assert.Equal(t, "/user2/repo1/pulls/2", test.RedirectURL(resp))
+
+	repoUnit := unittest.AssertExistsAndLoadBean(t, &repo_model.RepoUnit{RepoID: 1, Type: unit.TypeIssues})
+
+	// disable issue unit, it will be reset
+	_, err := db.DeleteByID[repo_model.RepoUnit](t.Context(), repoUnit.ID)
+	assert.NoError(t, err)
+
+	// even if the issue unit is disabled, visiting an issue which is a pull request
+	// will still redirect to pull request
+	req = NewRequest(t, "GET", "/user2/repo1/issues/2")
+	resp = session.MakeRequest(t, req, http.StatusSeeOther)
+	assert.Equal(t, "/user2/repo1/pulls/2", test.RedirectURL(resp))
 }
 
 func TestSearchIssues(t *testing.T) {