diff --git a/include/linux/if_ether.h b/include/linux/if_ether.h
index 7a1e011..42dc6a3 100644
--- a/include/linux/if_ether.h
+++ b/include/linux/if_ether.h
@@ -129,7 +129,7 @@
 /*
  *	Display a 6 byte device address (MAC) in a readable format.
  */
-extern char *print_mac(char *buf, const unsigned char *addr);
+extern __pure char *print_mac(char *buf, const unsigned char *addr);
 #define MAC_BUF_SIZE	18
 #define DECLARE_MAC_BUF(var) char var[MAC_BUF_SIZE] __maybe_unused