diff --git a/include/dos_system.h b/include/dos_system.h
index 9026d07b..4f5fd72c 100644
--- a/include/dos_system.h
+++ b/include/dos_system.h
@@ -78,6 +78,7 @@ public:
 	virtual void	AddRef()					{ refCtr++; };
 	virtual Bits	RemoveRef()					{ return --refCtr; };
 	virtual bool	UpdateDateTimeFromHost()	{ return true; }
+	virtual void SetFlagReadOnlyMedium() {}
 	void SetDrive(Bit8u drv) { hdrive=drv;}
 	Bit8u GetDrive(void) { return hdrive;}
 	Bit32u flags;
@@ -130,8 +131,8 @@ public:
 	bool Close                  (void);
 	Bit16u GetInformation       (void);
 	bool UpdateDateTimeFromHost (void);
-	void FlagReadOnlyMedium     (void);
 	void Flush                  (void);
+	void SetFlagReadOnlyMedium  () { read_only_medium = true; }
 	FILE * fhandle; //todo handle this properly
 private:
 	bool read_only_medium;
diff --git a/src/dos/drive_local.cpp b/src/dos/drive_local.cpp
index e3810327..1fac1aaa 100644
--- a/src/dos/drive_local.cpp
+++ b/src/dos/drive_local.cpp
@@ -520,10 +520,6 @@ localFile::localFile(const char* _name, FILE * handle) {
 	SetName(_name);
 }
 
-void localFile::FlagReadOnlyMedium(void) {
-	read_only_medium = true;
-}
-
 bool localFile::UpdateDateTimeFromHost(void) {
 	if(!open) return false;
 	struct stat temp_stat;
@@ -572,9 +568,10 @@ bool cdromDrive::FileOpen(DOS_File * * file,char * name,Bit32u flags) {
 		DOS_SetError(DOSERR_ACCESS_DENIED);
 		return false;
 	}
-	bool retcode = localDrive::FileOpen(file,name,flags);
-	if(retcode) (dynamic_cast<localFile*>(*file))->FlagReadOnlyMedium();
-	return retcode;
+	bool success = localDrive::FileOpen(file, name, flags);
+	if (success)
+		(*file)->SetFlagReadOnlyMedium();
+	return success;
 }
 
 bool cdromDrive::FileCreate(DOS_File * * /*file*/,char * /*name*/,Bit16u /*attributes*/) {