4 files changed, 13 insertions, 6 deletions
diff --git a/src/script/cpp_api/s_base.h b/src/script/cpp_api/s_base.h
index 06df2abe3..244d81605 100644
--- a/src/script/cpp_api/s_base.h
+++ b/src/script/cpp_api/s_base.h
@@ -125,6 +125,15 @@ protected:
 	friend class ModApiEnvMod;
 	friend class LuaVoxelManip;
 
+	/*
+		Subtle edge case with coroutines: If for whatever reason you have a
+		method in a subclass that's called from existing lua_CFunction
+		(any of the l_*.cpp files) then make it static and take the lua_State*
+		as an argument. This is REQUIRED because getStack() will not return the
+		correct state if called inside coroutines.
+
+		Also note that src/script/common/ is the better place for such helpers.
+	*/
 	lua_State* getStack()
 		{ return m_luastack; }
 
diff --git a/src/script/cpp_api/s_server.cpp b/src/script/cpp_api/s_server.cpp
index 6ddb2630d..c255b0c71 100644
--- a/src/script/cpp_api/s_server.cpp
+++ b/src/script/cpp_api/s_server.cpp
@@ -198,10 +198,8 @@ std::string ScriptApiServer::formatChatMessage(const std::string &name,
 	return ret;
 }
 
-u32 ScriptApiServer::allocateDynamicMediaCallback(int f_idx)
+u32 ScriptApiServer::allocateDynamicMediaCallback(lua_State *L, int f_idx)
 {
-	lua_State *L = getStack();
-
 	if (f_idx < 0)
 		f_idx = lua_gettop(L) + f_idx + 1;
 
@@ -235,7 +233,7 @@ u32 ScriptApiServer::allocateDynamicMediaCallback(int f_idx)
 
 void ScriptApiServer::freeDynamicMediaCallback(u32 token)
 {
-	lua_State *L = getStack();
+	SCRIPTAPI_PRECHECKHEADER
 
 	verbosestream << "freeDynamicMediaCallback(" << token << ")" << std::endl;
 
diff --git a/src/script/cpp_api/s_server.h b/src/script/cpp_api/s_server.h
index c5c3d5596..58c8c0e48 100644
--- a/src/script/cpp_api/s_server.h
+++ b/src/script/cpp_api/s_server.h
@@ -51,7 +51,7 @@ public:
 		const std::string &password);
 
 	/* dynamic media handling */
-	u32 allocateDynamicMediaCallback(int f_idx);
+	static u32 allocateDynamicMediaCallback(lua_State *L, int f_idx);
 	void freeDynamicMediaCallback(u32 token);
 	void on_dynamic_media_added(u32 token, const char *playername);
 
diff --git a/src/script/lua_api/l_server.cpp b/src/script/lua_api/l_server.cpp
index 82a692070..88ab5e16b 100644
--- a/src/script/lua_api/l_server.cpp
+++ b/src/script/lua_api/l_server.cpp
@@ -496,7 +496,7 @@ int ModApiServer::l_dynamic_add_media(lua_State *L)
 
 	CHECK_SECURE_PATH(L, filepath.c_str(), false);
 
-	u32 token = server->getScriptIface()->allocateDynamicMediaCallback(2);
+	u32 token = server->getScriptIface()->allocateDynamicMediaCallback(L, 2);
 
 	bool ok = server->dynamicAddMedia(filepath, token, to_player, ephemeral);
 	if (!ok)