diff --git a/include/mimalloc/internal.h b/include/mimalloc/internal.h
index 51fad09c..c9362aa0 100644
--- a/include/mimalloc/internal.h
+++ b/include/mimalloc/internal.h
@@ -96,7 +96,7 @@ uintptr_t   _mi_os_random_weak(uintptr_t extra_seed);
 static inline uintptr_t _mi_random_shuffle(uintptr_t x);
 
 // init.c
-extern mi_decl_cache_align mi_stats_t       _mi_stats_main;
+extern mi_decl_hidden mi_decl_cache_align mi_stats_t       _mi_stats_main;
 extern mi_decl_hidden mi_decl_cache_align const mi_page_t  _mi_page_empty;
 void        _mi_process_load(void);
 void mi_cdecl _mi_process_done(void);
@@ -958,8 +958,8 @@ static inline size_t mi_popcount(size_t x) {
 
 #if !MI_TRACK_ENABLED && defined(_WIN32) && (defined(_M_IX86) || defined(_M_X64))
 #include <intrin.h>
-extern bool _mi_cpu_has_fsrm;
-extern bool _mi_cpu_has_erms;
+extern mi_decl_hidden bool _mi_cpu_has_fsrm;
+extern mi_decl_hidden bool _mi_cpu_has_erms;
 static inline void _mi_memcpy(void* dst, const void* src, size_t n) {
   if ((_mi_cpu_has_fsrm && n <= 128) || (_mi_cpu_has_erms && n > 128)) {
     __movsb((unsigned char*)dst, (const unsigned char*)src, n);
diff --git a/include/mimalloc/prim.h b/include/mimalloc/prim.h
index a722d721..527bb97a 100644
--- a/include/mimalloc/prim.h
+++ b/include/mimalloc/prim.h
@@ -273,8 +273,8 @@ static inline void mi_prim_tls_slot_set(size_t slot, void* value) mi_attr_noexce
 #ifdef _MSC_VER
 __declspec(selectany)  // make it part of the comdat section to have faster TLS access (issue #1078)
 #endif
-extern mi_decl_thread mi_heap_t* _mi_heap_default;  // default heap to allocate from
-extern bool _mi_process_is_initialized;             // has mi_process_init been called?
+extern mi_decl_hidden mi_decl_thread mi_heap_t* _mi_heap_default;  // default heap to allocate from
+extern mi_decl_hidden bool _mi_process_is_initialized;             // has mi_process_init been called?
 
 static inline mi_threadid_t _mi_prim_thread_id(void) mi_attr_noexcept;
 
@@ -402,7 +402,7 @@ static inline mi_heap_t* mi_prim_get_default_heap(void) {
 
 #elif defined(MI_TLS_PTHREAD)
 
-extern pthread_key_t _mi_heap_default_key;
+extern mi_decl_hidden pthread_key_t _mi_heap_default_key;
 static inline mi_heap_t* mi_prim_get_default_heap(void) {
   mi_heap_t* heap = (mi_unlikely(_mi_heap_default_key == (pthread_key_t)(-1)) ? _mi_heap_main_get() : (mi_heap_t*)pthread_getspecific(_mi_heap_default_key));
   return (mi_unlikely(heap == NULL) ? (mi_heap_t*)&_mi_heap_empty : heap);
diff --git a/src/page.c b/src/page.c
index 6a693e89..55150f33 100644
--- a/src/page.c
+++ b/src/page.c
@@ -114,7 +114,7 @@ static bool mi_page_is_valid_init(mi_page_t* page) {
   return true;
 }
 
-extern bool _mi_process_is_initialized;             // has mi_process_init been called?
+extern mi_decl_hidden bool _mi_process_is_initialized;             // has mi_process_init been called?
 
 bool _mi_page_is_valid(mi_page_t* page) {
   mi_assert_internal(mi_page_is_valid_init(page));
@@ -979,9 +979,9 @@ void* _mi_malloc_generic(mi_heap_t* heap, size_t size, bool zero, size_t huge_al
 
     // free delayed frees from other threads (but skip contended ones)
     _mi_heap_delayed_free_partial(heap);
-    
+
     // collect every once in a while (10000 by default)
-    const long generic_collect = mi_option_get_clamp(mi_option_generic_collect, 1, 1000000L);    
+    const long generic_collect = mi_option_get_clamp(mi_option_generic_collect, 1, 1000000L);
     if (heap->generic_collect_count >= generic_collect) {
       heap->generic_collect_count = 0;
       mi_heap_collect(heap, false /* force? */);