diff --git a/include/mimalloc.h b/include/mimalloc.h
index 713ddd53..b14cba52 100644
--- a/include/mimalloc.h
+++ b/include/mimalloc.h
@@ -307,8 +307,8 @@ mi_decl_export bool mi_abandoned_visit_blocks(mi_subproc_id_t subproc_id, int he
 mi_decl_export void mi_heap_guarded_set_sample_rate(mi_heap_t* heap, size_t sample_rate, size_t seed);
 mi_decl_export void mi_heap_guarded_set_size_bound(mi_heap_t* heap, size_t min, size_t max);
 
-// Experimental: communicate that the thread associated with the heap runs in a threadpool
-mi_decl_export void mi_heap_set_in_threadpool(void) mi_attr_noexcept;  
+// Experimental: communicate that the thread is part of a threadpool
+mi_decl_export void mi_thread_set_in_threadpool(void) mi_attr_noexcept;  
 
 // Experimental: create a new heap with a specified heap tag. Set `allow_destroy` to false to allow the thread
 // to reclaim abandoned memory (with a compatible heap_tag and arena_id) but in that case `mi_heap_destroy` will
diff --git a/src/heap.c b/src/heap.c
index dffd915c..daad8afc 100644
--- a/src/heap.c
+++ b/src/heap.c
@@ -166,10 +166,6 @@ mi_heap_t* mi_heap_get_backing(void) {
   return bheap;
 }
 
-void mi_heap_set_in_threadpool(void) mi_attr_noexcept {
-  // nothing
-}
-
 // todo: make order of parameters consistent (but would that break compat with CPython?)
 void _mi_heap_init(mi_heap_t* heap, mi_arena_id_t arena_id, bool allow_destroy, uint8_t heap_tag, mi_tld_t* tld)
 {
diff --git a/src/init.c b/src/init.c
index 31b0d271..870e5ea4 100644
--- a/src/init.c
+++ b/src/init.c
@@ -602,6 +602,12 @@ void _mi_heap_set_default_direct(mi_heap_t* heap)  {
   _mi_prim_thread_associate_default_heap(heap);
 }
 
+void mi_thread_set_in_threadpool(void) mi_attr_noexcept {
+  mi_tld_t* tld = mi_tld();
+  if (tld!=NULL) { 
+    tld->is_in_threadpool = true;
+  }
+}
 
 // --------------------------------------------------------
 // Run functions on process init/done, and thread init/done