diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index db697c0..7b77503 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6164,6 +6164,14 @@
         sigfillset(&sigmask);
         sigprocmask(SIG_BLOCK, &sigmask, &info.sigmask);
 
+        /* If this is our first additional thread, we need to ensure we
+         * generate code for parallel execution and flush old translations.
+         */
+        if (!parallel_cpus) {
+            parallel_cpus = true;
+            tb_flush(cpu);
+        }
+
         ret = pthread_create(&info.thread, &attr, clone_func, &info);
         /* TODO: Free new CPU state if thread creation failed.  */