diff --git a/src/arena.c b/src/arena.c
index 4e030dd4..d64b8cdd 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -124,3 +124,11 @@ void arena_set_readonly(struct arena *arena)
     arena->readonly = true;
 #endif
 }
+
+void arena_set_readwrite(struct arena *arena)
+{
+#if RTC
+    arena->readonly = false;
+#endif
+    sys_memory_set_committed_readwrite(arena->base, arena->committed);
+}
diff --git a/src/arena.h b/src/arena.h
index 38e7e1d0..36b84894 100644
--- a/src/arena.h
+++ b/src/arena.h
@@ -33,6 +33,7 @@ void *_arena_push_bytes(struct arena *arena, u64 size, u64 align);
 void arena_copy_replace(struct arena *dest, struct arena *src);
 void arena_decommit_unused_blocks(struct arena *arena);
 void arena_set_readonly(struct arena *arena);
+void arena_set_readwrite(struct arena *arena);
 
 INLINE void *_arena_push_bytes_zero(struct arena *arena, u64 size, u64 align)
 {
diff --git a/src/sys.h b/src/sys.h
index df5e708b..2840a843 100644
--- a/src/sys.h
+++ b/src/sys.h
@@ -168,6 +168,7 @@ void *sys_memory_commit(void *address, u64 size);
 void sys_memory_decommit(void *address, u64 size);
 
 void sys_memory_set_committed_readonly(void *address, u64 size);
+void sys_memory_set_committed_readwrite(void *address, u64 size);
 
 /* ========================== *
  * Time
diff --git a/src/sys_win32.c b/src/sys_win32.c
index da3e64e7..644c85b2 100644
--- a/src/sys_win32.c
+++ b/src/sys_win32.c
@@ -208,10 +208,16 @@ void sys_memory_decommit(void *address, u64 size)
 
 void sys_memory_set_committed_readonly(void *address, u64 size)
 {
-    DWORD old = PAGE_READWRITE;
+    DWORD old;
     VirtualProtect(address, size, PAGE_READONLY, &old);
 }
 
+void sys_memory_set_committed_readwrite(void *address, u64 size)
+{
+    DWORD old;
+    VirtualProtect(address, size, PAGE_READWRITE, &old);
+}
+
 /* ========================== *
  * Time
  * ========================== */