diff --git a/README.md b/README.md
index 341194a..020c0e3 100644
--- a/README.md
+++ b/README.md
@@ -103,7 +103,7 @@ itself uses:
 
 ## Building from source
 
-This project uses [Go modules](https://go.dev/blog/using-go-modules) and requires Go 1.26+.
+This project uses [Go modules](https://go.dev/blog/using-go-modules) and requires Go 1.26.5+.
 
 ```bash
 go mod download
diff --git a/go.mod b/go.mod
index b5de66c..3bfd271 100644
--- a/go.mod
+++ b/go.mod
@@ -1,8 +1,6 @@
 module env-aws-params
 
-go 1.26
-
-toolchain go1.26.5
+go 1.26.5
 
 require (
 	github.com/aws/aws-sdk-go-v2 v1.41.7
diff --git a/main.go b/main.go
index f9ef265..ee837c1 100644
--- a/main.go
+++ b/main.go
@@ -29,6 +29,11 @@ func main() {
 		Flags:        cliFlags(),
 		Action:       action,
 		StopOnNthArg: &stopOnFirstArg,
+		// Flag parsing errors never reach action, so they are mapped to
+		// the documented usage-error exit code here.
+		OnUsageError: func(_ context.Context, _ *cli.Command, err error, _ bool) error {
+			return cli.Exit(errorPrefix(err), 125)
+		},
 	}
 	if err := cmd.Run(context.Background(), os.Args); err != nil {
 		log.Fatal(err)