diff --git a/src/init.c b/src/init.c
index 7cef8eea..1643d3fe 100644
--- a/src/init.c
+++ b/src/init.c
@@ -99,7 +99,7 @@ const mi_page_t _mi_page_empty = {
 // may lead to allocation itself on some platforms)
 // --------------------------------------------------------
 
-mi_decl_cache_align const mi_heap_t _mi_heap_empty = {
+mi_decl_hidden mi_decl_cache_align const mi_heap_t _mi_heap_empty = {
   NULL,
   MI_ATOMIC_VAR_INIT(NULL),
   0,                // tid
@@ -127,7 +127,7 @@ mi_threadid_t _mi_thread_id(void) mi_attr_noexcept {
 // the thread-local default heap for allocation
 mi_decl_thread mi_heap_t* _mi_heap_default = (mi_heap_t*)&_mi_heap_empty;
 
-extern mi_heap_t _mi_heap_main;
+extern mi_decl_hidden mi_heap_t _mi_heap_main;
 
 static mi_decl_cache_align mi_subproc_t mi_subproc_default;