diff --git a/memory/build/mozjemalloc.cpp b/memory/build/mozjemalloc.cpp
index 7a8211747f..874070d645 100644
--- a/memory/build/mozjemalloc.cpp
+++ b/memory/build/mozjemalloc.cpp
@@ -1450,7 +1450,7 @@ static size_t base_committed MOZ_GUARDED_BY(base_mtx);
// calling malloc to allocate storage on first access on each thread, which
// leads to an infinite loop, but pthread-based TLS somehow doesn't have this
// problem.
-#if !defined(XP_DARWIN)
+#if 0
static MOZ_THREAD_LOCAL(arena_t*) thread_arena;
#else
static detail::ThreadLocal<arena_t*, detail::ThreadLocalKeyStorage>