diff --git a/src/mod_mqtt.erl b/src/mod_mqtt.erl
index c76d910a4..e0e0a58e3 100644
--- a/src/mod_mqtt.erl
+++ b/src/mod_mqtt.erl
@@ -204,7 +204,7 @@ mod_options(Host) ->
     [{match_retained_limit, 1000},
      {max_topic_depth, 8},
      {max_topic_aliases, 100},
-     {session_expiry, 300},
+     {session_expiry, timer:minutes(5)},
      {max_queue, 5000},
      {access_subscribe, []},
      {access_publish, []},
@@ -219,7 +219,9 @@ mod_options(Host) ->
 mod_opt_type(max_queue) ->
     econf:pos_int(unlimited);
 mod_opt_type(session_expiry) ->
-    econf:non_neg_int();
+    econf:either(
+      econf:int(0, 0),
+      econf:timeout(second));
 mod_opt_type(match_retained_limit) ->
     econf:pos_int(infinity);
 mod_opt_type(max_topic_depth) ->
diff --git a/src/mod_mqtt_session.erl b/src/mod_mqtt_session.erl
index 0ac5be895..1c5a44649 100644
--- a/src/mod_mqtt_session.erl
+++ b/src/mod_mqtt_session.erl
@@ -36,9 +36,9 @@
 		peername              :: undefined | peername(),
 		timeout = infinity    :: timer(),
 		jid                   :: undefined | jid:jid(),
-		session_expiry = 0    :: seconds(),
+		session_expiry = 0    :: milli_seconds(),
 		will                  :: undefined | publish(),
-                will_delay = 0        :: seconds(),
+                will_delay = 0        :: milli_seconds(),
 		stop_reason           :: undefined | error_reason(),
 		acks = #{}            :: acks(),
 		subscriptions = #{}   :: subscriptions(),
@@ -178,7 +178,7 @@ handle_call({get_state, Pid}, From, State) ->
             ?DEBUG("Transferring MQTT session state to ~p at ~s", [Pid, node(Pid)]),
             Q1 = p1_queue:file_to_ram(State1#state.queue),
             p1_server:reply(From, {ok, State1#state{queue = Q1}}),
-            SessionExpiry = timer:seconds(State1#state.session_expiry),
+            SessionExpiry = State1#state.session_expiry,
             State2 = set_timeout(State1, min(SessionExpiry, ?RELAY_TIMEOUT)),
             State3 = State2#state{queue = undefined,
                                   stop_reason = {resumed, Pid},
@@ -348,7 +348,7 @@ handle_packet(#disconnect{code = Code, properties = Props},
     Reason = maps:get(reason_string, Props, <<>>),
     Expiry = case maps:get(session_expiry_interval, Props, undefined) of
                  undefined -> State#state.session_expiry;
-                 SE -> min(SE, session_expiry(Server))
+                 SE -> min(timer:seconds(SE), session_expiry(Server))
              end,
     State1 = State#state{session_expiry = Expiry},
     State2 = case Code of
@@ -407,13 +407,12 @@ stop(#state{session_expiry = SessExp} = State, Reason) ->
             State2 = if WillDelay == 0 ->
                              publish_will(State1);
                         WillDelay < SessExp ->
-                             erlang:start_timer(
-                               timer:seconds(WillDelay), self(), publish_will),
+                             erlang:start_timer(WillDelay, self(), publish_will),
                              State1;
                         true ->
                              State1
                      end,
-	    State3 = set_timeout(State2, timer:seconds(SessExp)),
+	    State3 = set_timeout(State2, SessExp),
 	    State4 = State3#state{stop_reason = Reason},
 	    noreply(State4)
     end.
@@ -656,7 +655,7 @@ set_session_properties(#state{version = Version,
                                 properties = Props} = Pkt) ->
     SEMin = case CleanStart of
                 false when Version == ?MQTT_VERSION_4 -> infinity;
-                _ -> maps:get(session_expiry_interval, Props, 0)
+                _ -> timer:seconds(maps:get(session_expiry_interval, Props, 0))
             end,
     SEConfig = session_expiry(Server),
     State1 = State#state{session_expiry = min(SEMin, SEConfig)},
@@ -671,7 +670,7 @@ set_will_properties(State, #connect{will = #publish{} = Will,
                               Ret -> Ret
                           end,
     State#state{will = Will#publish{properties = Props1},
-                will_delay = WillDelay};
+                will_delay = timer:seconds(WillDelay)};
 set_will_properties(State, _) ->
     State.
 
@@ -683,7 +682,7 @@ get_connack_properties(#state{session_expiry = SessExp, jid = JID},
                  <<>> -> #{assigned_client_identifier => JID#jid.lresource};
                  _ -> #{}
              end,
-    Props1#{session_expiry_interval => SessExp,
+    Props1#{session_expiry_interval => SessExp div 1000,
             shared_subscription_available => false,
             topic_alias_maximum => topic_alias_maximum(JID#jid.lserver),
             server_keep_alive => KeepAlive}.
@@ -1072,7 +1071,7 @@ queue_type(Host) ->
 queue_limit(Host) ->
     mod_mqtt_opt:max_queue(Host).
 
--spec session_expiry(binary()) -> seconds().
+-spec session_expiry(binary()) -> milli_seconds().
 session_expiry(Host) ->
     mod_mqtt_opt:session_expiry(Host).