diff --git a/compiler-rt/lib/fuzzer/FuzzerUtil.h b/compiler-rt/lib/fuzzer/FuzzerUtil.h
--- a/compiler-rt/lib/fuzzer/FuzzerUtil.h
+++ b/compiler-rt/lib/fuzzer/FuzzerUtil.h
@@ -15,6 +15,7 @@
 #include "FuzzerBuiltinsMsvc.h"
 #include "FuzzerCommand.h"
 #include "FuzzerDefs.h"
+#include <unistd.h>
 
 namespace fuzzer {
 
@@ -94,7 +95,7 @@
   return static_cast<size_t>((sizeof(unsigned long long) * 8) - Clzll(X) - 1);
 }
 
-inline size_t PageSize() { return 4096; }
+inline size_t PageSize() { return getpagesize(); }
 inline uint8_t *RoundUpByPage(uint8_t *P) {
   uintptr_t X = reinterpret_cast<uintptr_t>(P);
   size_t Mask = PageSize() - 1;