diff --git a/src/io/example_test.go b/src/io/example_test.go
index 6d338acd14..a18df9feff 100644
--- a/src/io/example_test.go
+++ b/src/io/example_test.go
@@ -103,7 +103,9 @@ func ExampleReadFull() {
 }
 
 func ExampleWriteString() {
-	io.WriteString(os.Stdout, "Hello World")
+	if _, err := io.WriteString(os.Stdout, "Hello World"); err != nil {
+		log.Fatal(err)
+	}
 
 	// Output: Hello World
 }