diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index c29d75d8f1b124ee7706da2e145189eaf7c5b65e..090e9991ac2a288f31f378ad327b4c18a2b8ecba 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1304,7 +1304,9 @@ static void arp_format_neigh_entry(struct seq_file *seq,
 		hbuffer[k++] = hex_asc_lo(n->ha[j]);
 		hbuffer[k++] = ':';
 	}
-	hbuffer[--k] = 0;
+	if (k != 0)
+		--k;
+	hbuffer[k] = 0;
 #if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
 	}
 #endif