diff --git a/source/firm.c b/source/firm.c
index d864bd6..d2600f0 100755
--- a/source/firm.c
+++ b/source/firm.c
@@ -246,6 +246,8 @@ static inline u32 loadFirm(FirmwareType *firmType, FirmwareSource firmSource)
             if(firmSource != FIRMWARE_SYSNAND) 
                 error("An old unsupported EmuNAND has been detected.\nLuma3DS is unable to boot it");
 
+            if(BOOTCONFIG(5, 1)) error("SAFE_MODE is not supported on 1.x/2.x FIRM");
+
             *firmType = NATIVE_FIRM1X2X;
         }