diff --git a/libc/bionic/pthread_detach.cpp b/libc/bionic/pthread_detach.cpp
index 95f11ac..a8608e3 100644
--- a/libc/bionic/pthread_detach.cpp
+++ b/libc/bionic/pthread_detach.cpp
@@ -44,6 +44,12 @@
     return 0; // Already being joined; silently do nothing, like glibc.
   }
 
+  if (thread->tid == 0) {
+    // Already exited; clean up.
+    _pthread_internal_remove_locked(thread.get());
+    return 0;
+  }
+
   thread->attr.flags |= PTHREAD_ATTR_FLAG_DETACHED;
   return 0;
 }