diff --git a/lib/conntrack-private.h b/lib/conntrack-private.h
index 9a8ca39..85329e8 100644
--- a/lib/conntrack-private.h
+++ b/lib/conntrack-private.h
@@ -59,6 +59,9 @@ struct conn_key {
     uint8_t nw_proto;
 };
 
+/* Verify that nw_proto stays uint8_t as it's used to index into l4_protos[] */
+BUILD_ASSERT_DECL(sizeof(((struct conn_key *)0)->nw_proto) == sizeof(uint8_t));
+
 /* This is used for alg expectations; an expectation is a
  * context created in preparation for establishing a data
  * connection. The expectation is created by the control
diff --git a/lib/conntrack.c b/lib/conntrack.c
index 0cbc8f6..3597112 100644
--- a/lib/conntrack.c
+++ b/lib/conntrack.c
@@ -143,12 +143,7 @@ detect_ftp_ctl_type(const struct conn_lookup_ctx *ctx,
 static void
 expectation_clean(struct conntrack *ct, const struct conn_key *master_key);
 
-static struct ct_l4_proto *l4_protos[] = {
-    [IPPROTO_TCP] = &ct_proto_tcp,
-    [IPPROTO_UDP] = &ct_proto_other,
-    [IPPROTO_ICMP] = &ct_proto_icmp4,
-    [IPPROTO_ICMPV6] = &ct_proto_icmp6,
-};
+static struct ct_l4_proto *l4_protos[UINT8_MAX + 1];
 
 static void
 handle_ftp_ctl(struct conntrack *ct, const struct conn_lookup_ctx *ctx,
@@ -296,6 +291,7 @@ ct_print_conn_info(const struct conn *c, const char *log_msg,
 struct conntrack *
 conntrack_init(void)
 {
+    static struct ovsthread_once setup_l4_once = OVSTHREAD_ONCE_INITIALIZER;
     struct conntrack *ct = xzalloc(sizeof *ct);
 
     ovs_rwlock_init(&ct->resources_lock);
@@ -322,6 +318,18 @@ conntrack_init(void)
     ct->clean_thread = ovs_thread_create("ct_clean", clean_thread_main, ct);
     ct->ipf = ipf_init();
 
+    /* Initialize the l4 protocols. */
+    if (ovsthread_once_start(&setup_l4_once)) {
+        for (int i = 0; i < ARRAY_SIZE(l4_protos); i++) {
+            l4_protos[i] = &ct_proto_other;
+        }
+        /* IPPROTO_UDP uses ct_proto_other, so no need to initialize it. */
+        l4_protos[IPPROTO_TCP] = &ct_proto_tcp;
+        l4_protos[IPPROTO_ICMP] = &ct_proto_icmp4;
+        l4_protos[IPPROTO_ICMPV6] = &ct_proto_icmp6;
+
+        ovsthread_once_done(&setup_l4_once);
+    }
     return ct;
 }
 
@@ -1970,9 +1978,10 @@ extract_l4(struct conn_key *key, const void *data, size_t size, bool *related,
         return (!related || check_l4_icmp6(key, data, size, l3,
                 validate_checksum))
                && extract_l4_icmp6(key, data, size, related);
-    } else {
-        return false;
     }
+
+    /* For all other protocols we do not have L4 keys, so keep them zero */
+    return true;
 }
 
 static bool
@@ -2255,8 +2264,8 @@ nat_select_range_tuple(struct conntrack *ct, const struct conn *conn,
               conn->nat_info->nat_action & NAT_ACTION_SRC_PORT
           ? true : false;
     union ct_addr first_addr = ct_addr;
-    bool pat_enabled = conn->key.nw_proto != IPPROTO_ICMP &&
-                       conn->key.nw_proto != IPPROTO_ICMPV6;
+    bool pat_enabled = conn->key.nw_proto == IPPROTO_TCP ||
+                       conn->key.nw_proto == IPPROTO_UDP;
 
     while (true) {
         if (conn->nat_info->nat_action & NAT_ACTION_SRC) {
diff --git a/tests/system-traffic.at b/tests/system-traffic.at
index 3ed03d9..b7aca93 100644
--- a/tests/system-traffic.at
+++ b/tests/system-traffic.at
@@ -2341,6 +2341,35 @@ NXST_FLOW reply:
 OVS_TRAFFIC_VSWITCHD_STOP
 AT_CLEANUP
 
+AT_SETUP([conntrack - generic IP protocol])
+CHECK_CONNTRACK()
+OVS_TRAFFIC_VSWITCHD_START()
+AT_CHECK([ovs-appctl vlog/set dpif:dbg dpif_netdev:dbg ofproto_dpif_upcall:dbg])
+
+ADD_NAMESPACES(at_ns0, at_ns1)
+
+ADD_VETH(p0, at_ns0, br0, "10.1.1.1/24")
+ADD_VETH(p1, at_ns1, br0, "10.1.1.2/24")
+
+AT_DATA([flows.txt], [dnl
+table=0, priority=1,action=drop
+table=0, priority=10,arp,action=normal
+table=0, priority=100,ip,action=ct(table=1)
+table=1, priority=100,in_port=1,ip,ct_state=+trk+new,action=ct(commit)
+table=1, priority=100,in_port=1,ct_state=+trk+est,action=normal
+])
+
+AT_CHECK([ovs-ofctl --bundle add-flows br0 flows.txt])
+
+AT_CHECK([ovs-ofctl -O OpenFlow13 packet-out br0 "in_port=1 packet=01005e00001200005e000101080045c0002800000000ff7019cdc0a8001ee0000012210164010001ba52c0a800010000000000000000000000000000 actions=resubmit(,0)"])
+
+AT_CHECK([ovs-appctl dpctl/dump-conntrack | grep "orig=.src=192\.168\.0\.30,"], [], [dnl
+112,orig=(src=192.168.0.30,dst=224.0.0.18,sport=0,dport=0),reply=(src=224.0.0.18,dst=192.168.0.30,sport=0,dport=0)
+])
+
+OVS_TRAFFIC_VSWITCHD_STOP
+AT_CLEANUP
+
 AT_SETUP([conntrack - ICMP related])
 AT_SKIP_IF([test $HAVE_NC = no])
 CHECK_CONNTRACK()
