diff --git a/sys/net/network_layer/icmpv6/icmpv6_hdr_print.c b/sys/net/network_layer/icmpv6/icmpv6_hdr_print.c
index 867e42fb8ea97531adbbcb1b381f3fe524ed807a..130e2fbf2a4a563e6f8ff73c8543cd50332a971d 100644
--- a/sys/net/network_layer/icmpv6/icmpv6_hdr_print.c
+++ b/sys/net/network_layer/icmpv6/icmpv6_hdr_print.c
@@ -22,6 +22,6 @@
 void icmpv6_hdr_print(icmpv6_hdr_t *hdr)
 {
     printf("   type: %3" PRIu8 "  code: %3" PRIu8 "\n", hdr->type, hdr->code);
-    printf("   cksum: 0x4%" PRIx16 "\n", byteorder_ntohs(hdr->csum));
+    printf("   cksum: 0x%04" PRIx16 "\n", byteorder_ntohs(hdr->csum));
 }
 /** @} */
diff --git a/sys/net/transport_layer/udp/udp_hdr_print.c b/sys/net/transport_layer/udp/udp_hdr_print.c
index 757a00ba6ed0cfc9840e54eee4cede863f6c62c0..0d22ae84f758f0c22ed6341106ef0ac599992ca8 100644
--- a/sys/net/transport_layer/udp/udp_hdr_print.c
+++ b/sys/net/transport_layer/udp/udp_hdr_print.c
@@ -27,6 +27,6 @@ void udp_hdr_print(udp_hdr_t *hdr)
 {
     printf("   src-port: %5" PRIu16 "  dst-port: %5" PRIu16 "\n",
            byteorder_ntohs(hdr->src_port), byteorder_ntohs(hdr->dst_port));
-    printf("   length: %" PRIu16 "  cksum: 0x4%" PRIx16 "\n",
+    printf("   length: %" PRIu16 "  cksum: 0x%04" PRIx16 "\n",
            byteorder_ntohs(hdr->length), byteorder_ntohs(hdr->checksum));
 }