diff --git a/src/Common/Apidrvr.h b/src/Common/Apidrvr.h
index d78e96db..4fc15767 100644
--- a/src/Common/Apidrvr.h
+++ b/src/Common/Apidrvr.h
@@ -322,7 +322,7 @@ typedef struct
 
 #define NT_MOUNT_PREFIX DRIVER_STR("\\Device\\VeraCryptVolume")
 #define NT_ROOT_PREFIX DRIVER_STR("\\Device\\VeraCrypt")
-#define DOS_MOUNT_PREFIX DRIVER_STR("\\DosDevices\\")
+#define DOS_MOUNT_PREFIX DRIVER_STR("\\GLOBAL??\\") // Explicitely use Global MS-DOS device names to avoid security issues
 #define DOS_ROOT_PREFIX DRIVER_STR("\\DosDevices\\VeraCrypt")
 #define WIN32_ROOT_PREFIX DRIVER_STR("\\\\.\\VeraCrypt")
 
diff --git a/src/Driver/Ntdriver.c b/src/Driver/Ntdriver.c
index 8c33a89c..3e78fabe 100644
--- a/src/Driver/Ntdriver.c
+++ b/src/Driver/Ntdriver.c
@@ -3063,18 +3063,19 @@ BOOL IsDriveLetterAvailable (int nDosDriveNo)
 	UNICODE_STRING objectName;
 	WCHAR link[128];
 	HANDLE handle;
+	NTSTATUS ntStatus;
 
 	TCGetDosNameFromNumber (link, sizeof(link),nDosDriveNo);
 	RtlInitUnicodeString (&objectName, link);
 	InitializeObjectAttributes (&objectAttributes, &objectName, OBJ_KERNEL_HANDLE | OBJ_CASE_INSENSITIVE, NULL, NULL);
 
-	if (NT_SUCCESS (ZwOpenSymbolicLinkObject (&handle, GENERIC_READ, &objectAttributes)))
+	if (NT_SUCCESS (ntStatus = ZwOpenSymbolicLinkObject (&handle, GENERIC_READ, &objectAttributes)))
 	{
 		ZwClose (handle);
 		return FALSE;
 	}
 
-	return TRUE;
+	return (ntStatus == STATUS_OBJECT_NAME_NOT_FOUND)? TRUE : FALSE;
 }