diff --git a/Core/FileSystems/MetaFileSystem.cpp b/Core/FileSystems/MetaFileSystem.cpp
index 2a3ec02f7b..19bddf251e 100644
--- a/Core/FileSystems/MetaFileSystem.cpp
+++ b/Core/FileSystems/MetaFileSystem.cpp
@@ -286,15 +286,25 @@ void MetaFileSystem::Unmount(std::string prefix, IFileSystem *system) {
 	fileSystems.erase(std::remove(fileSystems.begin(), fileSystems.end(), x), fileSystems.end());
 }
 
-void MetaFileSystem::Remount(std::string prefix, IFileSystem *newSystem, bool delOldSystem) {
+void MetaFileSystem::Remount(std::string prefix, IFileSystem *newSystem) {
 	std::lock_guard<std::recursive_mutex> guard(lock);
+	IFileSystem *oldSystem = nullptr;
 	for (auto &it : fileSystems) {
 		if (it.prefix == prefix) {
-			if (delOldSystem)
-				delete it.system;
+			oldSystem = it.system;
 			it.system = newSystem;
 		}
 	}
+
+	bool delOldSystem = true;
+	for (auto &it : fileSystems) {
+		if (it.system == oldSystem) {
+			delOldSystem = false;
+		}
+	}
+
+	if (delOldSystem)
+		delete oldSystem;
 }
 
 IFileSystem *MetaFileSystem::GetSystemFromFilename(const std::string &filename) {
diff --git a/Core/FileSystems/MetaFileSystem.h b/Core/FileSystems/MetaFileSystem.h
index 3fa2d16063..c4bfd8d37f 100644
--- a/Core/FileSystems/MetaFileSystem.h
+++ b/Core/FileSystems/MetaFileSystem.h
@@ -52,7 +52,7 @@ public:
 
 	void Mount(std::string prefix, IFileSystem *system);
 	void Unmount(std::string prefix, IFileSystem *system);
-	void Remount(std::string prefix, IFileSystem *newSystem, bool delOldSystem = true);
+	void Remount(std::string prefix, IFileSystem *newSystem);
 
 	IFileSystem *GetSystem(const std::string &prefix);
 	IFileSystem *GetSystemFromFilename(const std::string &filename);
diff --git a/Core/HLE/sceIo.cpp b/Core/HLE/sceIo.cpp
index ef4ca333e2..d200bb4e0f 100644
--- a/Core/HLE/sceIo.cpp
+++ b/Core/HLE/sceIo.cpp
@@ -1977,9 +1977,6 @@ static int sceIoChangeAsyncPriority(int id, int priority) {
 		return hleLogSuccessI(SCEIO, 0);
 	}
 
-	if (priority == -1)
-		priority = KernelCurThreadPriority();
-
 	u32 error;
 	FileNode *f = __IoGetFd(id, error);
 	if (!f) {
diff --git a/Core/HLE/sceUmd.cpp b/Core/HLE/sceUmd.cpp
index dcdfd88d93..3ebbaef092 100644
--- a/Core/HLE/sceUmd.cpp
+++ b/Core/HLE/sceUmd.cpp
@@ -495,7 +495,7 @@ static u32 sceUmdGetErrorStat()
 }
 
 void __UmdReplace(std::string filepath) {
-	char *error = "";
+	std::string error = "";
 	if (!UmdReplace(filepath, error)) {
 		ERROR_LOG(SCEIO, "UMD Replace failed: %s", error);
 		return;
diff --git a/Core/Loaders.cpp b/Core/Loaders.cpp
index dd898f4ac9..a4d102e122 100644
--- a/Core/Loaders.cpp
+++ b/Core/Loaders.cpp
@@ -356,7 +356,7 @@ bool LoadFile(FileLoader **fileLoaderPtr, std::string *error_string) {
 	return false;
 }
 
-bool UmdReplace(std::string filepath, char *error) {
+bool UmdReplace(std::string filepath, std::string &error) {
 	IFileSystem* currentUMD = pspFileSystem.GetSystem("disc0:");
 
 	if (!currentUMD) {
@@ -368,7 +368,7 @@ bool UmdReplace(std::string filepath, char *error) {
 
 	if (!loadedFile->Exists()) {
 		delete loadedFile;
-		sprintf(error, "%s doesn't exist", loadedFile->Path().c_str());
+		error = loadedFile->Path() + " doesn't exist";
 		return false;
 	}
 	UpdateLoadedFile(loadedFile);
@@ -387,7 +387,7 @@ bool UmdReplace(std::string filepath, char *error) {
 
 		break;
 	default:
-		sprintf(error, "Unsupported file type: %i", type);
+		error = "Unsupported file type:" + std::to_string((int)type);
 		return false;
 		break;
 	}
diff --git a/Core/Loaders.h b/Core/Loaders.h
index 9d114b446d..a076cfa675 100644
--- a/Core/Loaders.h
+++ b/Core/Loaders.h
@@ -159,4 +159,4 @@ void RegisterFileLoaderFactory(std::string name, std::unique_ptr<FileLoaderFacto
 // Can modify the string filename, as it calls IdentifyFile above.
 bool LoadFile(FileLoader **fileLoaderPtr, std::string *error_string);
 
-bool UmdReplace(std::string filepath, char* error);
+bool UmdReplace(std::string filepath, std::string &error);
diff --git a/Core/PSPLoaders.cpp b/Core/PSPLoaders.cpp
index f53707ae26..1f1425fe2c 100644
--- a/Core/PSPLoaders.cpp
+++ b/Core/PSPLoaders.cpp
@@ -83,7 +83,7 @@ void InitMemoryForGameISO(FileLoader *fileLoader) {
 
 	IFileSystem *fileSystem = nullptr;
 	IFileSystem *blockSystem = nullptr;
-	//bool actualIso = false;
+
 	if (fileLoader->IsDirectory()) {
 		fileSystem = new VirtualDiscFileSystem(&pspFileSystem, fileLoader->Path());
 		blockSystem = fileSystem;
@@ -155,8 +155,7 @@ bool ReInitMemoryForGameISO(FileLoader *fileLoader) {
 	if (fileLoader->IsDirectory()) {
 		fileSystem = new VirtualDiscFileSystem(&pspFileSystem, fileLoader->Path());
 		blockSystem = fileSystem;
-	}
-	else {
+	} else {
 		auto bd = constructBlockDevice(fileLoader);
 		if (!bd)
 			return false;
@@ -166,15 +165,11 @@ bool ReInitMemoryForGameISO(FileLoader *fileLoader) {
 		blockSystem = new ISOBlockSystem(iso);
 	}
 
-	if (pspFileSystem.GetSystem("disc0:") != pspFileSystem.GetSystem("umd0:")) {
-		// We mounted an ISO block system separately.
-		pspFileSystem.Remount("umd0:", blockSystem, false);
-		pspFileSystem.Remount("umd1:", blockSystem, false);
+		pspFileSystem.Remount("umd0:", blockSystem);
+		pspFileSystem.Remount("umd1:", blockSystem);
 		pspFileSystem.Remount("umd:", blockSystem);
-	}
-	
-	pspFileSystem.Remount("disc0:", fileSystem);
-	
+		pspFileSystem.Remount("disc0:", fileSystem);
+
 	return true;
 }