diff --git a/src/scripting/decorate/thingdef_parse.cpp b/src/scripting/decorate/thingdef_parse.cpp
index d3d6335516..24360b165c 100644
--- a/src/scripting/decorate/thingdef_parse.cpp
+++ b/src/scripting/decorate/thingdef_parse.cpp
@@ -77,7 +77,7 @@ PClassActor *DecoDerivedClass(const FScriptPosition &sc, PClassActor *parent, FN
 	if (type == nullptr)
 	{
 		FString newname = typeName.GetChars();
-		FString sourcefile = sc.FileName;
+		FString sourcefile = sc.FileName.GetChars();
 
 		sourcefile.Substitute(":", "@");
 		newname << '@' << sourcefile;
@@ -1342,4 +1342,4 @@ void ParseAllDecorate()
 		auto ns = Namespaces.NewNamespace(sc.LumpNum);
 		ParseDecorate(sc, ns);
 	}
-}
\ No newline at end of file
+}