diff --git a/mfbt/Poison.cpp b/mfbt/Poison.cpp
index f806df61aae9..b2767011d5fb 100644
--- a/mfbt/Poison.cpp
+++ b/mfbt/Poison.cpp
@@ -129,7 +129,7 @@ ReleaseRegion(void* aRegion, uintptr_t aSize)
 static bool
 ProbeRegion(uintptr_t aRegion, uintptr_t aSize)
 {
-  if (posix_madvise(reinterpret_cast<void*>(aRegion), aSize, POSIX_MADV_NORMAL)) {
+  if (madvise(reinterpret_cast<void*>(aRegion), aSize, MADV_NORMAL)) {
     return true;
   } else {
     return false;
diff --git a/mfbt/tests/TestPoisonArea.cpp b/mfbt/tests/TestPoisonArea.cpp
index af997f73c927..76af23f69437 100644
--- a/mfbt/tests/TestPoisonArea.cpp
+++ b/mfbt/tests/TestPoisonArea.cpp
@@ -269,7 +269,7 @@ ReleaseRegion(void* aPage)
 static bool
 ProbeRegion(uintptr_t aPage)
 {
-  return !!posix_madvise(reinterpret_cast<void*>(aPage), PageSize(), POSIX_MADV_NORMAL);
+  return !!madvise(reinterpret_cast<void*>(aPage), PageSize(), MADV_NORMAL);
 }
 
 static int