diff --git a/vm/code_heap.hpp b/vm/code_heap.hpp
index aed5a2bd13..fd125bae01 100755
--- a/vm/code_heap.hpp
+++ b/vm/code_heap.hpp
@@ -41,6 +41,8 @@ struct code_heap {
 	void clear_mark_bits();
 	void free(code_block *compiled);
 	void flush_icache();
+	void guard_safepoint();
+	void unguard_safepoint();
 };
 
 struct code_heap_room {
diff --git a/vm/os-unix.cpp b/vm/os-unix.cpp
index 91aca6e7be..7045a073bb 100755
--- a/vm/os-unix.cpp
+++ b/vm/os-unix.cpp
@@ -124,6 +124,18 @@ segment::~segment()
 		fatal_error("Segment deallocation failed",0);
 }
 
+void code_heap::guard_safepoint()
+{
+	if(mprotect(safepoint_page,getpagesize(),PROT_NONE) == -1)
+		fatal_error("Cannot protect safepoint guard page",(cell)safepoint_page);
+}
+
+void code_heap::unguard_safepoint()
+{
+	if(mprotect(safepoint_page,getpagesize(),PROT_WRITE) == -1)
+		fatal_error("Cannot unprotect safepoint guard page",(cell)safepoint_page);
+}
+
 void factor_vm::dispatch_signal(void *uap, void (handler)())
 {
 	UAP_STACK_POINTER(uap) = (UAP_STACK_POINTER_TYPE)fix_callstack_top((stack_frame *)UAP_STACK_POINTER(uap));
diff --git a/vm/os-windows.cpp b/vm/os-windows.cpp
index 795a80e5c7..3dc6da7863 100755
--- a/vm/os-windows.cpp
+++ b/vm/os-windows.cpp
@@ -148,6 +148,20 @@ long getpagesize()
 	return g_pagesize;
 }
 
+void code_heap::guard_safepoint()
+{
+	DWORD ignore;
+	if (!VirtualProtect(safepoint_page, getpagesize(), PAGE_NOACCESS, &ignore))
+		fatal_error("Cannot protect safepoint guard page", (cell)safepoint_page);
+}
+
+void code_heap::unguard_safepoint()
+{
+	DWORD ignore;
+	if (!VirtualProtect(safepoint_page, getpagesize(), PAGE_READWRITE, &ignore))
+		fatal_error("Cannot unprotect safepoint guard page", (cell)safepoint_page);
+}
+
 void factor_vm::move_file(const vm_char *path1, const vm_char *path2)
 {
 	if(MoveFileEx((path1),(path2),MOVEFILE_REPLACE_EXISTING) == false)