diff --git a/libc/include/netinet/ether.h b/libc/include/netinet/ether.h
index 480063d..d570c18 100644
--- a/libc/include/netinet/ether.h
+++ b/libc/include/netinet/ether.h
@@ -44,7 +44,7 @@
  *
  * Returns a pointer to a static buffer.
  */
-char* ether_ntoa(const struct ether_addr* __addr);
+char* _Nonnull ether_ntoa(const struct ether_addr* _Nonnull __addr);
 
 /**
  * [ether_ntoa_r(3)](http://man7.org/linux/man-pages/man3/ether_ntoa_r.3.html) returns a string
@@ -52,7 +52,7 @@
  *
  * Returns a pointer to the given buffer.
  */
-char* ether_ntoa_r(const struct ether_addr* __addr, char* __buf);
+char* _Nonnull ether_ntoa_r(const struct ether_addr* _Nonnull __addr, char* _Nonnull __buf);
 
 /**
  * [ether_aton(3)](http://man7.org/linux/man-pages/man3/ether_aton.3.html) returns an `ether_addr`
@@ -60,7 +60,7 @@
  *
  * Returns a pointer to a static buffer, or NULL if the given string isn't a valid MAC address.
  */
-struct ether_addr* ether_aton(const char* __ascii);
+struct ether_addr* _Nullable ether_aton(const char* _Nonnull __ascii);
 
 /**
  * [ether_aton_r(3)](http://man7.org/linux/man-pages/man3/ether_aton_r.3.html) returns an
@@ -68,6 +68,6 @@
  *
  * Returns a pointer to the given buffer, or NULL if the given string isn't a valid MAC address.
  */
-struct ether_addr* ether_aton_r(const char* __ascii, struct ether_addr* __addr);
+struct ether_addr* _Nullable ether_aton_r(const char* _Nonnull __ascii, struct ether_addr* _Nonnull __addr);
 
 __END_DECLS