diff --git a/__test__/connect.spec.mjs b/__test__/connect.spec.mjs
index 99ab0d5..f50cafd 100644
--- a/__test__/connect.spec.mjs
+++ b/__test__/connect.spec.mjs
@@ -142,7 +142,7 @@ test("forward number", async (t) => {
   await validateShutdown(t, httpServer, url);
 });
 
-test("forward port string", async (t) => {
+test("forward just string as port", async (t) => {
   ngrok.consoleLog();
   const httpServer = await makeHttp();
   ngrok.authtoken(process.env["NGROK_AUTHTOKEN"]);
@@ -166,6 +166,18 @@ test("forward addr port string", async (t) => {
   await validateShutdown(t, httpServer, url);
 });
 
+test("forward port string", async (t) => {
+  ngrok.consoleLog();
+  const httpServer = await makeHttp();
+  ngrok.authtoken(process.env["NGROK_AUTHTOKEN"]);
+  const listener = await ngrok.forward({ port: httpServer.listenTo.split(":")[1] });
+  const url = listener.url();
+
+  t.truthy(url);
+  t.truthy(url.startsWith("https://"), url);
+  await validateShutdown(t, httpServer, url);
+});
+
 test("forward string", async (t) => {
   const httpServer = await makeHttp();
   ngrok.authtoken(process.env["NGROK_AUTHTOKEN"]);
diff --git a/index.js b/index.js
index 7954a77..2737613 100644
--- a/index.js
+++ b/index.js
@@ -545,6 +545,13 @@ async function ngrokForward(config) {
     }
     config = { addr: address };
   }
+  if (typeof config["port"] === "string" || config["port"] instanceof String) {
+    const num = parseInt(config["port"]);
+    if (isNaN(num)) {
+      throw new Error(`port must be a number: '${config["port"]}'`);
+    }
+    config["port"] = num;
+  }
   // Convert addr to string to allow for numeric port numbers
   const addr = config["addr"];
   if (Number.isInteger(addr)) config["addr"] = "localhost:" + String(config["addr"]);
diff --git a/trailer.js b/trailer.js
index d98180d..e3f7df8 100644
--- a/trailer.js
+++ b/trailer.js
@@ -272,6 +272,13 @@ async function ngrokForward(config) {
     }
     config = { addr: address };
   }
+  if (typeof config["port"] === "string" || config["port"] instanceof String) {
+    const num = parseInt(config["port"]);
+    if (isNaN(num)) {
+      throw new Error(`port must be a number: '${config["port"]}'`);
+    }
+    config["port"] = num;
+  }
   // Convert addr to string to allow for numeric port numbers
   const addr = config["addr"];
   if (Number.isInteger(addr)) config["addr"] = "localhost:" + String(config["addr"]);