diff --git a/libc/bionic/pthread_internal.cpp b/libc/bionic/pthread_internal.cpp
index c058384..870a526 100644
--- a/libc/bionic/pthread_internal.cpp
+++ b/libc/bionic/pthread_internal.cpp
@@ -88,7 +88,7 @@
 static void __pthread_internal_free(pthread_internal_t* thread) {
   if (thread->mmap_size != 0) {
     // Free mapped space, including thread stack and pthread_internal_t.
-    munmap(thread->attr.stack_base, thread->mmap_size);
+    munmap(thread->mmap_base, thread->mmap_size);
   }
 }