diff --git a/libc/malloc_debug/PointerData.cpp b/libc/malloc_debug/PointerData.cpp
index 5542c1e..6c7d8fa 100644
--- a/libc/malloc_debug/PointerData.cpp
+++ b/libc/malloc_debug/PointerData.cpp
@@ -601,9 +601,9 @@
 }
 
 void PointerData::PrepareFork() NO_THREAD_SAFETY_ANALYSIS {
+  free_pointer_mutex_.lock();
   pointer_mutex_.lock();
   frame_mutex_.lock();
-  free_pointer_mutex_.lock();
 }
 
 void PointerData::PostForkParent() NO_THREAD_SAFETY_ANALYSIS {