diff --git a/src/g_game.cpp b/src/g_game.cpp
index 1d9b73950..6490ab25e 100644
--- a/src/g_game.cpp
+++ b/src/g_game.cpp
@@ -2859,17 +2859,17 @@ bool G_CheckDemoStatus (void)
 	return false; 
 }
 
-void G_StartSlideshow(FName whichone)
+void G_StartSlideshow(FLevelLocals *Level, FName whichone)
 {
 	gameaction = ga_slideshow;
-	SelectedSlideshow = whichone == NAME_None ? level.info->slideshow : whichone;
+	SelectedSlideshow = whichone == NAME_None ? Level->info->slideshow : whichone;
 }
 
 DEFINE_ACTION_FUNCTION(FLevelLocals, StartSlideshow)
 {
-	PARAM_PROLOGUE;
+	PARAM_SELF_STRUCT_PROLOGUE(FLevelLocals);
 	PARAM_NAME(whichone);
-	G_StartSlideshow(whichone);
+	G_StartSlideshow(self, whichone);
 	return 0;
 }
 
diff --git a/src/g_game.h b/src/g_game.h
index b1b18d5c8..119c531e3 100644
--- a/src/g_game.h
+++ b/src/g_game.h
@@ -68,7 +68,7 @@ void G_Ticker (void);
 bool G_Responder (event_t*	ev);
 
 void G_ScreenShot (char *filename);
-void G_StartSlideshow(FName whichone);
+void G_StartSlideshow(FLevelLocals *Level, FName whichone);
 
 FString G_BuildSaveName (const char *prefix, int slot);
 
diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index d6285bff8..2c675d0b0 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -6619,7 +6619,7 @@ doplaysound:			if (funcIndex == ACSF_PlayActorSound)
 			return ScriptCall(activator, argCount, args);
 
 		case ACSF_StartSlideshow:
-			G_StartSlideshow(FName(Level->Behaviors.LookupString(args[0])));
+			G_StartSlideshow(Level, FName(Level->Behaviors.LookupString(args[0])));
 			break;
 
 		case ACSF_GetSectorHealth: