diff --git a/src/nu/nusicallbackadd.c b/src/nu/nusicallbackadd.c
index a30f9cd..18f1bf1 100644
--- a/src/nu/nusicallbackadd.c
+++ b/src/nu/nusicallbackadd.c
@@ -1,3 +1,24 @@
 #include "common.h"
 
-INCLUDE_ASM(const s32, "nu/nusicallbackadd", nuSiCallBackAdd);
+#include "nu/nusys.h"
+
+void nuSiCallBackAdd(NUCallBackList* list) {
+    OSIntMask mask;
+    NUCallBackList** siCallBackListPtr = &nuSiCallBackList;
+    u32 i;
+
+    while (*siCallBackListPtr != NULL) {
+        if ((*siCallBackListPtr)->majorNo == list->majorNo) {
+            return;
+        }
+        siCallBackListPtr = &(*siCallBackListPtr)->next;
+    }
+
+    for (i = 1; list->func[i] != NULL; i++);
+
+    mask = osSetIntMask(OS_IM_NONE);
+    *siCallBackListPtr = list;
+    list->next = NULL;
+    list->funcNum = i;
+    osSetIntMask(mask);
+}
\ No newline at end of file