diff --git a/lib/core/src/server/cli/dev.js b/lib/core/src/server/cli/dev.js
index 04a589e07cd1..9dab960414f1 100644
--- a/lib/core/src/server/cli/dev.js
+++ b/lib/core/src/server/cli/dev.js
@@ -57,6 +57,10 @@ async function getCLI(packageJson) {
     configDir: 'SBCONFIG_CONFIG_DIR',
   });
 
+  if (typeof program.port === 'string' && program.port.length > 0) {
+    program.port = parseInt(program.port, 10);
+  }
+
   const port = await getFreePort(program.port);
 
   if (!program.ci && !program.smokeTest && program.port != null && port !== program.port) {