diff --git a/sys/netinet6/in6_mcast.c b/sys/netinet6/in6_mcast.c
--- a/sys/netinet6/in6_mcast.c
+++ b/sys/netinet6/in6_mcast.c
@@ -346,6 +346,22 @@
 	return (MCAST_PASS);
 }
 
+struct in6_multi *
+in6m_lookup_locked(struct ifnet *ifp, const struct in6_addr *mcaddr)
+{
+	struct ifmultiaddr *ifma;
+	struct in6_multi *inm;
+
+	CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
+		inm = in6m_ifmultiaddr_get_inm(ifma);
+		if (inm == NULL)
+			continue;
+		if (IN6_ARE_ADDR_EQUAL(&inm->in6m_addr, mcaddr))
+			return (inm);
+	}
+	return (NULL);
+}
+
 /*
  * Find and return a reference to an in6_multi record for (ifp, group),
  * and bump its reference count.
diff --git a/sys/netinet6/in6_var.h b/sys/netinet6/in6_var.h
--- a/sys/netinet6/in6_var.h
+++ b/sys/netinet6/in6_var.h
@@ -790,21 +790,8 @@
  *
  * SMPng: The IN6_MULTI_LOCK and must be held and must be in network epoch.
  */
-static __inline struct in6_multi *
-in6m_lookup_locked(struct ifnet *ifp, const struct in6_addr *mcaddr)
-{
-	struct ifmultiaddr *ifma;
-	struct in6_multi *inm;
-
-	CK_STAILQ_FOREACH(ifma, &ifp->if_multiaddrs, ifma_link) {
-		inm = in6m_ifmultiaddr_get_inm(ifma);
-		if (inm == NULL)
-			continue;
-		if (IN6_ARE_ADDR_EQUAL(&inm->in6m_addr, mcaddr))
-			return (inm);
-	}
-	return (NULL);
-}
+struct in6_multi *
+in6m_lookup_locked(struct ifnet *ifp, const struct in6_addr *mcaddr);
 
 /*
  * Wrapper for in6m_lookup_locked().