diff --git a/sys/netinet/ip_divert.c b/sys/netinet/ip_divert.c
--- a/sys/netinet/ip_divert.c
+++ b/sys/netinet/ip_divert.c
@@ -220,9 +220,6 @@
 	}
 #if defined(SCTP) || defined(SCTP_SUPPORT)
 	if (m->m_pkthdr.csum_flags & CSUM_SCTP) {
-		m = mb_unmapped_to_ext(m);
-		if (m == NULL)
-			return;
 		sctp_delayed_cksum(m, (uint32_t)(ip->ip_hl << 2));
 		m->m_pkthdr.csum_flags &= ~CSUM_SCTP;
 	}
@@ -238,9 +235,6 @@
 	}
 #if defined(SCTP) || defined(SCTP_SUPPORT)
 	if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6) {
-		m = mb_unmapped_to_ext(m);
-		if (m == NULL)
-			return;
 		sctp_delayed_cksum(m, sizeof(struct ip6_hdr));
 		m->m_pkthdr.csum_flags &= ~CSUM_SCTP_IPV6;
 	}
diff --git a/sys/netinet/ip_output.c b/sys/netinet/ip_output.c
--- a/sys/netinet/ip_output.c
+++ b/sys/netinet/ip_output.c
@@ -753,12 +753,6 @@
 	}
 #if defined(SCTP) || defined(SCTP_SUPPORT)
 	if (m->m_pkthdr.csum_flags & CSUM_SCTP & ~ifp->if_hwassist) {
-		m = mb_unmapped_to_ext(m);
-		if (m == NULL) {
-			IPSTAT_INC(ips_odropped);
-			error = ENOBUFS;
-			goto bad;
-		}
 		sctp_delayed_cksum(m, (uint32_t)(ip->ip_hl << 2));
 		m->m_pkthdr.csum_flags &= ~CSUM_SCTP;
 	}
@@ -911,12 +905,6 @@
 	}
 #if defined(SCTP) || defined(SCTP_SUPPORT)
 	if (m0->m_pkthdr.csum_flags & CSUM_SCTP) {
-		m0 = mb_unmapped_to_ext(m0);
-		if (m0 == NULL) {
-			error = ENOBUFS;
-			IPSTAT_INC(ips_odropped);
-			goto done;
-		}
 		sctp_delayed_cksum(m0, hlen);
 		m0->m_pkthdr.csum_flags &= ~CSUM_SCTP;
 	}
diff --git a/sys/netipsec/ipsec_output.c b/sys/netipsec/ipsec_output.c
--- a/sys/netipsec/ipsec_output.c
+++ b/sys/netipsec/ipsec_output.c
@@ -411,12 +411,6 @@
 		if (m->m_pkthdr.csum_flags & CSUM_SCTP) {
 			struct ip *ip;
 
-			m = mb_unmapped_to_ext(m);
-			if (m == NULL) {
-				IPSECSTAT_INC(ips_out_nomem);
-				key_freesp(&sp);
-				return (ENOBUFS);
-			}
 			ip = mtod(m, struct ip *);
 			sctp_delayed_cksum(m, (uint32_t)(ip->ip_hl << 2));
 			m->m_pkthdr.csum_flags &= ~CSUM_SCTP;
@@ -791,12 +785,6 @@
 		}
 #if defined(SCTP) || defined(SCTP_SUPPORT)
 		if (m->m_pkthdr.csum_flags & CSUM_SCTP_IPV6) {
-			m = mb_unmapped_to_ext(m);
-			if (m == NULL) {
-				IPSEC6STAT_INC(ips_out_nomem);
-				key_freesp(&sp);
-				return (ENOBUFS);
-			}
 			sctp_delayed_cksum(m, sizeof(struct ip6_hdr));
 			m->m_pkthdr.csum_flags &= ~CSUM_SCTP_IPV6;
 		}
diff --git a/sys/netpfil/pf/pf.c b/sys/netpfil/pf/pf.c
--- a/sys/netpfil/pf/pf.c
+++ b/sys/netpfil/pf/pf.c
@@ -6000,9 +6000,6 @@
 	}
 #if defined(SCTP) || defined(SCTP_SUPPORT)
 	if (m0->m_pkthdr.csum_flags & CSUM_SCTP & ~ifp->if_hwassist) {
-		m0 = mb_unmapped_to_ext(m0);
-		if (m0 == NULL)
-			goto done;
 		sctp_delayed_cksum(m0, (uint32_t)(ip->ip_hl << 2));
 		m0->m_pkthdr.csum_flags &= ~CSUM_SCTP;
 	}