diff --git a/source/disc.c b/source/disc.c
index d27da2a..5f22b49 100755
--- a/source/disc.c
+++ b/source/disc.c
@@ -87,10 +87,11 @@ const INTERFACE_ID _FAT_disc_interfaces[] = {
 /* ====================== NDS ====================== */
 #elif defined (NDS)
 #include <nds/system.h>
+#include <nds/memory.h>
 #include <nds/arm9/dldi.h>
 
 static const DISC_INTERFACE* get_io_dsisd (void) {
-	return isDSiMode() ? &__io_dsisd : NULL;
+	return (isDSiMode() && __NDSHeader->unitCode ) ? &__io_dsisd : NULL;
 }
 
 const INTERFACE_ID _FAT_disc_interfaces[] = {