diff --git a/sbin/ipfw/ipfw.c b/sbin/ipfw/ipfw.c
index af71e1e5bde7..407540e8365d 100644
--- a/sbin/ipfw/ipfw.c
+++ b/sbin/ipfw/ipfw.c
@@ -95,7 +95,7 @@ static struct icmpcode icmpcodes[] = {
       { 0, NULL }
 };
 
-static void show_usage(const char *fmt, ...);
+static void show_usage(const char *fmt, ...) __printf0like(1, 2);
 
 static int
 mask_bits(struct in_addr m_ad)
@@ -275,7 +275,7 @@ show_ipfw(struct ip_fw *chain)
 			he = gethostbyaddr((char *)&adrt,
 			    sizeof(u_long), AF_INET);
 			if (he == NULL)
-				printf(inet_ntoa(chain->fw_src));
+				printf("%s", inet_ntoa(chain->fw_src));
 			else
 				printf("%s", he->h_name);
 		} else if (adrt != ULONG_MAX) {
@@ -283,15 +283,15 @@ show_ipfw(struct ip_fw *chain)
 			if (mb == 0) {
 				printf("any");
 			} else if (mb > 0) {
-				printf(inet_ntoa(chain->fw_src));
+				printf("%s", inet_ntoa(chain->fw_src));
 				printf("/%d", mb);
 			} else {
-				printf(inet_ntoa(chain->fw_src));
+				printf("%s", inet_ntoa(chain->fw_src));
 				printf(":");
-				printf(inet_ntoa(chain->fw_smsk));
+				printf("%s", inet_ntoa(chain->fw_smsk));
 			}
 		} else {
-			printf(inet_ntoa(chain->fw_src));
+			printf("%s", inet_ntoa(chain->fw_src));
 		}
 	}
 
@@ -320,7 +320,7 @@ show_ipfw(struct ip_fw *chain)
 			he = gethostbyaddr((char *)&adrt,
 			    sizeof(u_long), AF_INET);
 			if (he == NULL)
-				printf(inet_ntoa(chain->fw_dst));
+				printf("%s", inet_ntoa(chain->fw_dst));
 			else
 				printf("%s", he->h_name);
 		} else if (adrt != ULONG_MAX) {
@@ -328,15 +328,15 @@ show_ipfw(struct ip_fw *chain)
 			if (mb == 0) {
 				printf("any");
 			} else if (mb > 0) {
-				printf(inet_ntoa(chain->fw_dst));
+				printf("%s", inet_ntoa(chain->fw_dst));
 				printf("/%d", mb);
 			} else {
-				printf(inet_ntoa(chain->fw_dst));
+				printf("%s", inet_ntoa(chain->fw_dst));
 				printf(":");
-				printf(inet_ntoa(chain->fw_dmsk));
+				printf("%s", inet_ntoa(chain->fw_dmsk));
 			}
 		} else {
-			printf(inet_ntoa(chain->fw_dst));
+			printf("%s", inet_ntoa(chain->fw_dst));
 		}
 	}