diff --git a/vpsdk/dynlib.vp b/vpsdk/dynlib.vp
index 2cb6a04..dc84f1f 100644
--- a/vpsdk/dynlib.vp
+++ b/vpsdk/dynlib.vp
@@ -4,5 +4,8 @@ from . import syscall as syscall
 def load_so(path: const str) -> uint64:
     return syscall._syscall1(uint64(syscall.LOAD_SO), uint64(path))
 
-def so_call1(sym_name: const str, arg1: t.CPtr) -> int:
+def so_call1(sym_name: const str, arg1: rawptr) -> int:
+    # arg1 只是原样交给系统调用的裸地址，故用 rawptr（未定/通配指针）而非 t.CPtr：
+    # 后者是具体类型的一级指针，调用方传字符串字面量（二级指针）会被判成级数不符
+    # （CastError: pointer level differs, source level 2 -> target level 1）。
     return int(syscall._syscall2(uint64(syscall.SO_CALL1), uint64(sym_name), uint64(arg1)))