diff --git a/sys/netinet/sctputil.c b/sys/netinet/sctputil.c
index 6c251deb35fa..98b11bf65a88 100644
--- a/sys/netinet/sctputil.c
+++ b/sys/netinet/sctputil.c
@@ -831,7 +831,7 @@ sctp_get_prev_mtu(uint32_t val)
 {
 	uint32_t i;
 
-	val &= 0x00000003;
+	val &= 0xfffffffc;
 	if (val <= sctp_mtu_sizes[0]) {
 		return (val);
 	}
@@ -857,7 +857,7 @@ sctp_get_next_mtu(uint32_t val)
 	/* select another MTU that is just bigger than this one */
 	uint32_t i;
 
-	val &= 0x00000003;
+	val &= 0xfffffffc;
 	for (i = 0; i < (sizeof(sctp_mtu_sizes) / sizeof(uint32_t)); i++) {
 		if (val < sctp_mtu_sizes[i]) {
 			KASSERT((sctp_mtu_sizes[i] & 0x00000003) == 0,