diff --git a/user/user.h b/user/user.h
index 8ac6395..4d398d5 100644
--- a/user/user.h
+++ b/user/user.h
@@ -9,7 +9,7 @@ int write(int, const void*, int);
 int read(int, void*, int);
 int close(int);
 int kill(int);
-int exec(char*, char**);
+int exec(const char*, char**);
 int open(const char*, int);
 int mknod(const char*, short, short);
 int unlink(const char*);