diff --git a/libc/include/grp.h b/libc/include/grp.h
index b727562..9d67adf 100644
--- a/libc/include/grp.h
+++ b/libc/include/grp.h
@@ -47,19 +47,19 @@
 
 __BEGIN_DECLS
 
-struct group* getgrgid(gid_t);
-struct group* getgrnam(const char*);
+struct group* getgrgid(gid_t __gid);
+struct group* getgrnam(const char* __name);
 
 /* Note: Android has thousands and thousands of ids to iterate through. */
 struct group* getgrent(void) __INTRODUCED_IN(26);
 
 void setgrent(void) __INTRODUCED_IN(26);
 void endgrent(void) __INTRODUCED_IN(26);
-int getgrgid_r(gid_t, struct group*, char*, size_t, struct group**) __INTRODUCED_IN(24);
-int getgrnam_r(const char*, struct group*, char*, size_t, struct group**) __INTRODUCED_IN(24);
-int getgrouplist (const char*, gid_t, gid_t*, int*);
-int initgroups (const char*, gid_t);
+int getgrgid_r(gid_t __gid, struct group* __group, char* __buf, size_t __n, struct group** __result) __INTRODUCED_IN(24);
+int getgrnam_r(const char* __name, struct group* __group, char* __buf, size_t __n, struct group** __result) __INTRODUCED_IN(24);
+int getgrouplist(const char* __user, gid_t __group, gid_t* __groups, int* __group_count);
+int initgroups(const char* __user, gid_t __group);
 
 __END_DECLS
 
-#endif /* !_GRP_H_ */
+#endif