diff --git a/src/dobjgc.h b/src/dobjgc.h
index 9fbad404ec..ed0370728f 100644
--- a/src/dobjgc.h
+++ b/src/dobjgc.h
@@ -180,6 +180,20 @@ public:
 		return *this;
 	}
 
+	T operator=(nullptr_t nul)
+	{
+		o = nullptr;
+		return nullptr;
+	}
+
+	// To allow NULL, too.
+	T operator=(const int val)
+	{
+		assert(val == 0);
+		o = nullptr;
+		return nullptr;
+	}
+
 	operator T() throw()
 	{
 		return GC::ReadBarrier(pp);
diff --git a/src/p_acs.cpp b/src/p_acs.cpp
index 577ac1a459..648b8eae1f 100644
--- a/src/p_acs.cpp
+++ b/src/p_acs.cpp
@@ -765,33 +765,6 @@ private:
 	friend class DACSThinker;
 };
 
-class DACSThinker : public DThinker
-{
-	DECLARE_CLASS(DACSThinker, DThinker)
-	HAS_OBJECT_POINTERS
-public:
-	DACSThinker();
-	~DACSThinker();
-
-	void Serialize(FSerializer &arc);
-	void Tick();
-
-	typedef TMap<int, DLevelScript *> ScriptMap;
-	ScriptMap RunningScripts;	// Array of all synchronous scripts
-
-	void DumpScriptStatus();
-	void StopScriptsFor(AActor *actor);
-
-private:
-	DLevelScript *LastScript;
-	DLevelScript *Scripts;				// List of all running scripts
-
-	friend class DLevelScript;
-	friend class FBehavior;
-	friend struct FBehaviorContainer;
-};
-
-
 static DLevelScript *P_GetScriptGoing (AActor *who, line_t *where, int num, const ScriptPtr *code, FBehavior *module,
 	const int *args, int argcount, int flags);
 
diff --git a/src/p_acs.h b/src/p_acs.h
index 0c7f1b5837..f3c724353e 100644
--- a/src/p_acs.h
+++ b/src/p_acs.h
@@ -36,6 +36,7 @@
 #define __P_ACS_H__
 
 #include "doomtype.h"
+#include "dthinker.h"
 
 #define LOCAL_SIZE				20
 #define NUM_MAPVARS				128
@@ -445,6 +446,34 @@ struct FBehaviorContainer
 
 };
 
+class DLevelScript;
+
+class DACSThinker : public DThinker
+{
+	DECLARE_CLASS(DACSThinker, DThinker)
+	HAS_OBJECT_POINTERS
+public:
+	DACSThinker();
+	~DACSThinker();
+
+	void Serialize(FSerializer &arc);
+	void Tick();
+
+	typedef TMap<int, DLevelScript *> ScriptMap;
+	ScriptMap RunningScripts;	// Array of all synchronous scripts
+
+	void DumpScriptStatus();
+	void StopScriptsFor(AActor *actor);
+
+private:
+	DLevelScript *LastScript;
+	DLevelScript *Scripts;				// List of all running scripts
+
+	friend class DLevelScript;
+	friend class FBehavior;
+	friend struct FBehaviorContainer;
+};
+
 
 
 
diff --git a/src/p_saveg.cpp b/src/p_saveg.cpp
index 5b16797450..db93ef8d84 100644
--- a/src/p_saveg.cpp
+++ b/src/p_saveg.cpp
@@ -978,7 +978,7 @@ void G_SerializeLevel(FSerializer &arc, bool hubload)
 		.Array("level.bodyque", level.bodyque, level.BODYQUESIZE)
 		("level.corpsequeue", level.CorpseQueue)
 		("level.spotstate", level.SpotState)
-		("level.fragglethinker", level.FraggleScriptThinker);
+		("level.fragglethinker", level.FraggleScriptThinker)
 		("level.acsthinker", level.ACSThinker);
 
 	// Hub transitions must keep the current total time
diff --git a/src/p_setup.cpp b/src/p_setup.cpp
index 6a022fb061..3cd8792449 100644
--- a/src/p_setup.cpp
+++ b/src/p_setup.cpp
@@ -68,9 +68,10 @@
 #include "types.h"
 #include "i_time.h"
 #include "scripting/vm/vm.h"
-#include "fragglescript/t_fs.h"
 #include "a_specialspot.h"
 #include "maploader/maploader.h"
+#include "p_acs.h"
+#include "fragglescript/t_script.h"
 
 void P_ClearUDMFKeys();
 
@@ -275,6 +276,8 @@ void FLevelLocals::ClearLevelData()
 	ClearPortals();
 
 	SpotState = nullptr;
+	ACSThinker = nullptr;
+	FraggleScriptThinker = nullptr;
 	CorpseQueue.Clear();
 	canvasTextureInfo.EmptyList();
 	sections.Clear();