diff --git a/libc/bionic/malloc_common_dynamic.h b/libc/bionic/malloc_common_dynamic.h
index 8794ed0..755af8f 100644
--- a/libc/bionic/malloc_common_dynamic.h
+++ b/libc/bionic/malloc_common_dynamic.h
@@ -28,7 +28,8 @@
 
 #pragma once
 
-#include <stdbool.h>
+#include <pthread.h>
+#include <stdatomic.h>
 
 #include <private/bionic_globals.h>
 #include <private/bionic_malloc_dispatch.h>
@@ -40,3 +41,7 @@
 void* LoadSharedLibrary(const char* shared_lib, const char* prefix, MallocDispatch* dispatch_table);
 
 bool FinishInstallHooks(libc_globals* globals, const char* options, const char* prefix);
+
+// Lock for globals, to guarantee that only one thread is doing a mutate.
+extern pthread_mutex_t gGlobalsMutateLock;
+extern _Atomic bool gGlobalsMutating;