diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index c792289..86949de 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -97,9 +97,10 @@
 int execvp(const char* __file, char* const* __argv);
 int execvpe(const char* __file, char* const* __argv, char* const* __envp) __INTRODUCED_IN(21);
 int execve(const char* __file, char* const* __argv, char* const* __envp);
-int execl(const char* __path, const char* __arg0, ...);
-int execlp(const char* __file, const char* __arg0, ...);
-int execle(const char* __path, const char* __arg0, ...);
+int execl(const char* __path, const char* __arg0, ...) __attribute__((__sentinel__));
+int execlp(const char* __file, const char* __arg0, ...) __attribute__((__sentinel__));
+int execle(const char* __path, const char* __arg0, ... /*,  char* const* __envp */)
+    __attribute__((__sentinel__(1)));
 
 int nice(int __incr);