diff --git a/routers/api/v1/repo/branch.go b/routers/api/v1/repo/branch.go
index eb080e4367..a17f0ad40d 100644
--- a/routers/api/v1/repo/branch.go
+++ b/routers/api/v1/repo/branch.go
@@ -420,6 +420,7 @@ func UpdateBranch(ctx *context.APIContext) {
 	//   in: path
 	//   description: name of the branch
 	//   type: string
+	//   required: true
 	// - name: body
 	//   in: body
 	//   schema:
@@ -470,6 +471,12 @@ func UpdateBranch(ctx *context.APIContext) {
 
 	branch, err := ctx.Repo.GitRepo.GetBranch(branchName)
 	if err != nil {
+		if git.IsErrBranchNotExist(err) {
+			// This could occur if the client passes a non-existent branch and we
+			// skip executing the branch that contains the RenameBranch() call.
+			ctx.NotFound(err)
+			return
+		}
 		ctx.Error(http.StatusInternalServerError, "GetBranch", err)
 		return
 	}
diff --git a/templates/swagger/v1_json.tmpl b/templates/swagger/v1_json.tmpl
index 0cd377b2e6..b8006258c4 100644
--- a/templates/swagger/v1_json.tmpl
+++ b/templates/swagger/v1_json.tmpl
@@ -5025,7 +5025,8 @@
             "type": "string",
             "description": "name of the branch",
             "name": "branch",
-            "in": "path"
+            "in": "path",
+            "required": true
           },
           {
             "name": "body",
diff --git a/tests/integration/api_branch_test.go b/tests/integration/api_branch_test.go
index 80a9a66301..e2b3dc86fb 100644
--- a/tests/integration/api_branch_test.go
+++ b/tests/integration/api_branch_test.go
@@ -218,6 +218,9 @@ func TestAPIUpdateBranch(t *testing.T) {
 			branchWasUnchanged := slices.ContainsFunc(branches, func(b *git_model.Branch) bool { return b.Name == "master" })
 			assert.True(t, branchWasUnchanged, "master branch shouldn't have been renamed")
 		})
+		t.Run("UpdateBranchWithNonExistentBranchAndNewNameIsTheEmptyString", func(t *testing.T) {
+			testAPIUpdateBranch(t, "user2", "repo1", "i-dont-exist", "", http.StatusNotFound)
+		})
 		t.Run("RenameBranchNormalScenario", func(t *testing.T) {
 			resp := testAPIUpdateBranch(t, "user2", "repo1", "branch2", "new-branch-name", http.StatusOK)
 			var branch api.Branch