diff --git a/VM/include/lua.h b/VM/include/lua.h
index 8e7d6468..a158485a 100644
--- a/VM/include/lua.h
+++ b/VM/include/lua.h
@@ -358,6 +358,8 @@ struct lua_Callbacks
     void (*debugstep)(lua_State* L, lua_Debug* ar);      /* gets called after each instruction in single step mode */
     void (*debuginterrupt)(lua_State* L, lua_Debug* ar); /* gets called when thread execution is interrupted by break in another thread */
     void (*debugprotectederror)(lua_State* L);           /* gets called when protected call results in an error */
+
+    void (*gc)(lua_State* L); /* gets called when a garbage collection cycle starts */
 };
 
 LUA_API lua_Callbacks* lua_callbacks(lua_State* L);
diff --git a/VM/src/lgc.cpp b/VM/src/lgc.cpp
index 6553009f..501a68c3 100644
--- a/VM/src/lgc.cpp
+++ b/VM/src/lgc.cpp
@@ -617,6 +617,8 @@ static void markroot(lua_State* L)
     markvalue(g, registry(L));
     markmt(g);
     g->gcstate = GCSpropagate;
+    if (g->cb.gc)
+        g->cb.gc(L);
 }
 
 static size_t remarkupvals(global_State* g)