diff --git a/src/scripting/backend/codegen.cpp b/src/scripting/backend/codegen.cpp
index dc904b804..76414e235 100644
--- a/src/scripting/backend/codegen.cpp
+++ b/src/scripting/backend/codegen.cpp
@@ -8815,11 +8815,8 @@ ExpEmit FxVMFunctionCall::Emit(VMFunctionBuilder *build)
 			if (outerside == FScopeBarrier::Side_Virtual)
 				outerside = FScopeBarrier::SideFromObjectFlags(CallingFunction->OwningClass->ObjectFlags);
 
-			if (selfside != outerside && (selfside == FScopeBarrier::Side_Play || selfside == FScopeBarrier::Side_UI))	// if the self pointer and the calling functions have the same scope the check here is not needed.
-			{
-				// Check the self object against the calling function's flags at run time
-				build->Emit(OP_SCOPE, selfemit.RegNum, outerside + 1, build->GetConstantAddress(vmfunc, ATAG_OBJECT));
-			}
+			// Check the self object against the calling function's flags at run time
+			build->Emit(OP_SCOPE, selfemit.RegNum, outerside + 1, build->GetConstantAddress(vmfunc, ATAG_OBJECT));
 		}
 
 		if (selfemit.Fixed && selfemit.Target)
diff --git a/src/scripting/decorate/thingdef_parse.cpp b/src/scripting/decorate/thingdef_parse.cpp
index 05a927288..9ad5e0e67 100644
--- a/src/scripting/decorate/thingdef_parse.cpp
+++ b/src/scripting/decorate/thingdef_parse.cpp
@@ -97,6 +97,12 @@ PClassActor *DecoDerivedClass(const FScriptPosition &sc, PClassActor *parent, FN
 			sc.Message(MSG_FATAL, "Tried to define class '%s' more than twice in the same file.", typeName.GetChars());
 		}
 	}
+	else
+	{
+		// [ZZ] DECORATE classes are always play
+		type->ObjectFlags = FScopeBarrier::ChangeSideInObjectFlags(type->ObjectFlags, FScopeBarrier::Side_Play);
+	}
+
 	return type;
 }
 
diff --git a/src/scripting/vm/vmexec.h b/src/scripting/vm/vmexec.h
index b588d15d3..900d06ffa 100644
--- a/src/scripting/vm/vmexec.h
+++ b/src/scripting/vm/vmexec.h
@@ -648,10 +648,10 @@ begin:
 			reg.a[a] = p->Virtuals[C];
 		}
 		NEXTOP;
-	OP(SCOPE) :
-	{
-		ASSERTA(a); ASSERTA(C);
-		FScopeBarrier::ValidateCall(((DObject*)konsta[a].v)->GetClass(), (VMFunction*)konsta[C].v, B - 1);
+	OP(SCOPE):
+		{
+			ASSERTA(a); ASSERTKA(C);
+			FScopeBarrier::ValidateCall(((DObject*)reg.a[a])->GetClass(), (VMFunction*)konsta[C].v, B - 1);
 		}
 		NEXTOP;
 
diff --git a/src/scripting/zscript/zcc_compile.cpp b/src/scripting/zscript/zcc_compile.cpp
index 222c20a26..f18c3230f 100644
--- a/src/scripting/zscript/zcc_compile.cpp
+++ b/src/scripting/zscript/zcc_compile.cpp
@@ -658,12 +658,12 @@ void ZCCCompiler::CreateClassTypes()
 						{
 							Error(c->cls, "Can't change class scope in class %s", c->NodeName().GetChars());
 						}
-						c->Type()->ObjectFlags = (c->Type()->ObjectFlags & ~(OF_UI | OF_Play)) | (parent->ObjectFlags & (OF_UI | OF_Play));
+						c->Type()->ObjectFlags = FScopeBarrier::ChangeSideInObjectFlags(c->Type()->ObjectFlags, FScopeBarrier::SideFromObjectFlags(parent->ObjectFlags));
 					}
 				}
 				else
 				{
-					c->Type()->ObjectFlags = (c->Type()->ObjectFlags&~OF_UI) | OF_Play;
+					c->Type()->ObjectFlags = FScopeBarrier::ChangeSideInObjectFlags(c->Type()->ObjectFlags, FScopeBarrier::Side_Play);
 				}
 
 				c->Type()->bExported = true;	// this class is accessible to script side type casts. (The reason for this flag is that types like PInt need to be skipped.)