diff --git a/compiler-rt/lib/asan/asan_fuchsia.cpp b/compiler-rt/lib/asan/asan_fuchsia.cpp
--- a/compiler-rt/lib/asan/asan_fuchsia.cpp
+++ b/compiler-rt/lib/asan/asan_fuchsia.cpp
@@ -118,14 +118,12 @@
 
 // Shared setup between thread creation and startup for the initial thread.
 static AsanThread *CreateAsanThread(StackTrace *stack, u32 parent_tid,
-                                    uptr user_id, bool detached,
-                                    const char *name) {
+                                    bool detached, const char *name) {
   // In lieu of AsanThread::Create.
   AsanThread *thread = (AsanThread *)MmapOrDie(AsanThreadMmapSize(), __func__);
 
   AsanThreadContext::CreateThreadContextArgs args = {thread, stack};
-  u32 tid =
-      asanThreadRegistry().CreateThread(user_id, detached, parent_tid, &args);
+  u32 tid = asanThreadRegistry().CreateThread(0, detached, parent_tid, &args);
   asanThreadRegistry().SetThreadName(tid, name);
 
   return thread;
@@ -147,12 +145,11 @@
 
 // Called by __asan::AsanInitInternal (asan_rtl.c).
 AsanThread *CreateMainThread() {
-  thrd_t self = thrd_current();
   char name[ZX_MAX_NAME_LEN];
   CHECK_NE(__sanitizer::MainThreadStackBase, 0);
   CHECK_GT(__sanitizer::MainThreadStackSize, 0);
   AsanThread *t = CreateAsanThread(
-      nullptr, 0, reinterpret_cast<uptr>(self), true,
+      nullptr, 0, true,
       _zx_object_get_property(thrd_get_zx_handle(self), ZX_PROP_NAME, name,
                               sizeof(name)) == ZX_OK
           ? name
@@ -182,8 +179,7 @@
   GET_STACK_TRACE_THREAD;
   u32 parent_tid = GetCurrentTidOrInvalid();
 
-  AsanThread *thread =
-      CreateAsanThread(&stack, parent_tid, user_id, detached, name);
+  AsanThread *thread = CreateAsanThread(&stack, parent_tid, detached, name);
 
   // On other systems, AsanThread::Init() is called from the new
   // thread itself.  But on Fuchsia we already know the stack address
diff --git a/compiler-rt/lib/asan/asan_thread.cpp b/compiler-rt/lib/asan/asan_thread.cpp
--- a/compiler-rt/lib/asan/asan_thread.cpp
+++ b/compiler-rt/lib/asan/asan_thread.cpp
@@ -83,8 +83,7 @@
   thread->start_routine_ = start_routine;
   thread->arg_ = arg;
   AsanThreadContext::CreateThreadContextArgs args = {thread, stack};
-  asanThreadRegistry().CreateThread(*reinterpret_cast<uptr *>(thread), detached,
-                                    parent_tid, &args);
+  asanThreadRegistry().CreateThread(0, detached, parent_tid, &args);
 
   return thread;
 }