diff --git a/libc/bionic/clone.cpp b/libc/bionic/clone.cpp
index b50a96d..3a20aa9 100644
--- a/libc/bionic/clone.cpp
+++ b/libc/bionic/clone.cpp
@@ -38,6 +38,11 @@
 
 // Called from the __bionic_clone assembler to call the thread function then exit.
 extern "C" __LIBC_HIDDEN__ void __start_thread(int (*fn)(void*), void* arg) {
+  pthread_internal_t* self = __get_thread();
+  if (self && self->tid == -1) {
+    self->tid = syscall(__NR_gettid);
+  }
+
   int status = (*fn)(arg);
   __exit(status);
 }
@@ -105,6 +110,9 @@
     // If any other cases become important, we could use a double trampoline like __pthread_start.
     self->set_cached_pid(parent_pid);
     self->tid = caller_tid;
+  } else if (self->tid == -1) {
+    self->tid = syscall(__NR_gettid);
+    self->set_cached_pid(self->tid);
   }
 
   return clone_result;
diff --git a/libc/bionic/fork.cpp b/libc/bionic/fork.cpp
index ffe94f4..32ea255 100644
--- a/libc/bionic/fork.cpp
+++ b/libc/bionic/fork.cpp
@@ -36,9 +36,6 @@
 
   pthread_internal_t* self = __get_thread();
 
-  // Remember the parent pid and invalidate the cached value while we fork.
-  pid_t parent_pid = self->invalidate_cached_pid();
-
   int result = clone(nullptr,
                      nullptr,
                      (CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID | SIGCHLD),
@@ -47,10 +44,11 @@
                      nullptr,
                      &(self->tid));
   if (result == 0) {
+    // Update the cached pid, since clone() will not set it directly (as
+    // self->tid is updated by the kernel).
     self->set_cached_pid(gettid());
     __bionic_atfork_run_child();
   } else {
-    self->set_cached_pid(parent_pid);
     __bionic_atfork_run_parent();
   }
   return result;