diff --git a/include/mimalloc/prim.h b/include/mimalloc/prim.h
index 8d108100..cce9cfaf 100644
--- a/include/mimalloc/prim.h
+++ b/include/mimalloc/prim.h
@@ -168,7 +168,7 @@ static inline void* mi_prim_tls_slot(size_t slot) mi_attr_noexcept {
     #if defined(__APPLE__) // M1, issue #343
     __asm__ volatile ("mrs %0, tpidrro_el0\nbic %0, %0, #7" : "=r" (tcb));
     #else
-    //__asm__ volatile ("mrs %0, CTPIDR_EL0" : "=c" (tcb));
+    __asm__ volatile ("mrs %0, CTPIDR_EL0" : "=r" (tcb));
     //void *__capability tcb = __builtin_thread_pointer();
     #endif
     res = tcb[slot];