diff --git a/packages/next/src/cli/next-dev.ts b/packages/next/src/cli/next-dev.ts
index 9e4c7d2daaaf..93ce6da61d1f 100644
--- a/packages/next/src/cli/next-dev.ts
+++ b/packages/next/src/cli/next-dev.ts
@@ -327,7 +327,7 @@ const nextDev: CliCommand = async (argv) => {
         ...Object.keys(rawNextConfig).filter((key) =>
           checkUnsupportedCustomConfig(key, rawNextConfig, defaultConfig)
         ),
-        ...Object.keys(rawNextConfig.experimental)
+        ...Object.keys(rawNextConfig.experimental ?? [])
           .filter((key) =>
             checkUnsupportedCustomConfig(
               key,