diff --git a/packages/serve-cli/src/cli.ts b/packages/serve-cli/src/cli.ts
index 834c028f95518..0a62c62da4fd0 100644
--- a/packages/serve-cli/src/cli.ts
+++ b/packages/serve-cli/src/cli.ts
@@ -169,7 +169,7 @@ export type AddCommand = (ctx: CLIContext, cli: CLI) => void;
 
 // we dont use `Option.default()` in the command definitions because we want the CLI options to
 // override the config file (with option defaults, config file will always be overwritten)
-const maxAvailableFork = Math.max(availableParallelism() - 1, 1);
+const maxAvailableFork = availableParallelism();
 export const defaultOptions = {
   fork: process.env.NODE_ENV === 'production' ? maxAvailableFork : 1,
   host:
@@ -196,10 +196,7 @@ let cli = new Command()
       .env('FORK')
       .argParser(v => {
         const count = parseInt(v);
-        if (isNaN(count)) {
-          throw new InvalidArgumentError('not a number.');
-        }
-        if (count > maxAvailableFork) {
+        if (isNaN(count) || count > maxAvailableFork) {
           return maxAvailableFork;
         }
         return count;