diff --git a/include/mimalloc-internal.h b/include/mimalloc-internal.h
index dca21bb9..e1190c7e 100644
--- a/include/mimalloc-internal.h
+++ b/include/mimalloc-internal.h
@@ -734,7 +734,7 @@ static inline void mi_tls_slot_set(size_t slot, void* value) mi_attr_noexcept {
   tcb[slot] = value;
 #elif defined(__aarch64__)
   void** tcb; UNUSED(ofs);
-#if defined(__MACH__)
+#if defined(__APPLE__)
   __asm__ volatile ("mrs %0, tpidrro_el0" : "=r" (tcb));
 #else
   __asm__ volatile ("mrs %0, tpidr_el0" : "=r" (tcb));