Index: lib/libc/sys/fork.2
===================================================================
--- lib/libc/sys/fork.2
+++ lib/libc/sys/fork.2
@@ -118,13 +118,20 @@
 	case -1:
 		err(1, "Failed to fork");
 	case 0:
+		/*
+		 * Using stdio safely around fork() requires at least flushing buffers
+		 * and ensuring that opened FILEs are in some consistent state right
+		 * at fork.
+		 */
 		printf("Hello from child process!\en");
+		fflush(stdout);
 		exit(0);
 	default:
 		break;
 	}
 
 	printf("Hello from parent process (child's PID: %d)!\en", pid);
+	fflush(stdout);
 
 	return (0);
 }