diff --git a/src/init.c b/src/init.c
index f29480ce..2db21d3f 100644
--- a/src/init.c
+++ b/src/init.c
@@ -556,11 +556,14 @@ void mi_process_init(void) mi_attr_noexcept {
   mi_detect_cpu_features();
   _mi_os_init();
   mi_heap_main_init();
-  #if (MI_DEBUG)
+  #if MI_DEBUG
   _mi_verbose_message("debug level : %d\n", MI_DEBUG);
   #endif
   _mi_verbose_message("secure level: %d\n", MI_SECURE);
   _mi_verbose_message("mem tracking: %s\n", MI_TRACK_TOOL);
+  #if MI_TSAN
+  _mi_verbose_message("thread santizer enabled\n");
+  #endif
   mi_thread_init();
 
   #if defined(_WIN32)
diff --git a/src/os.c b/src/os.c
index 5a0035b9..d6c94b11 100644
--- a/src/os.c
+++ b/src/os.c
@@ -21,7 +21,7 @@ static mi_os_mem_config_t mi_os_mem_config = {
   0,      // large page size (usually 2MiB)
   4096,   // allocation granularity
   true,   // has overcommit?  (if true we use MAP_NORESERVE on mmap systems)
-  false   // must free whole?
+  false   // must free whole? (on mmap systems we can free anywhere in a mapped range, but on Windows we must free the entire span)
 };
 
 bool _mi_os_has_overcommit(void) {