diff --git a/zscript/vm.h b/zscript/vm.h
index 8a8b9e9f8..ee20d3ceb 100644
--- a/zscript/vm.h
+++ b/zscript/vm.h
@@ -104,6 +104,7 @@ enum
 	ATAG_SREGISTER,			// pointer to a string register
 	ATAG_AREGISTER,			// pointer to an address register
 
+	ATAG_STATE,				// pointer to FState
 };
 
 class VMFunction : public DObject
@@ -758,14 +759,14 @@ public:
 	void ParamObject(DObject *obj)
 	{
 		Reg.a[RegA] = obj;
-		Reg.atag[RegA] = true;
+		Reg.atag[RegA] = ATAG_OBJECT;
 		RegA++;
 	}
 
-	void ParamPointer(void *ptr)
+	void ParamPointer(void *ptr, VM_UBTYE atag)
 	{
 		Reg.a[RegA] = ptr;
-		Reg.atag[RegA] = false;
+		Reg.atag[RegA] = atag;
 		RegA++;
 	}
 
diff --git a/zscript/vmexec.h b/zscript/vmexec.h
index c0b268589..6bb2ae3eb 100644
--- a/zscript/vmexec.h
+++ b/zscript/vmexec.h
@@ -533,11 +533,14 @@ begin:
 		{ // No return values
 			return 0;
 		}
-		assert(a < numret);
-		SetReturn(reg, f, &ret[a], B, C);
+		assert(ret != NULL || numret == 0);
+		if (a < numret)
+		{
+			SetReturn(reg, f, &ret[a], B, C);
+		}
 		if (B & REGT_FINAL)
 		{
-			return a + 1;
+			return MIN(numret, a + 1);
 		}
 		NEXTOP;
 	OP(RESULT):