Index: lib/sanitizer_common/sanitizer_posix_libcdep.cc
===================================================================
--- lib/sanitizer_common/sanitizer_posix_libcdep.cc
+++ lib/sanitizer_common/sanitizer_posix_libcdep.cc
@@ -61,8 +61,10 @@
   uptr page_size = GetPageSizeCached();
   uptr beg_aligned = RoundUpTo(beg, page_size);
   uptr end_aligned = RoundDownTo(end, page_size);
+  const int madvise_flag =
+      (SANITIZER_FREEBSD || SANITIZER_MAC) ? MADV_FREE : MADV_DONTNEED;
   if (beg_aligned < end_aligned)
-    madvise((void*)beg_aligned, end_aligned - beg_aligned, MADV_DONTNEED);
+    madvise((void*)beg_aligned, end_aligned - beg_aligned, madvise_flag);
 }
 
 void NoHugePagesInRegion(uptr addr, uptr size) {