diff --git a/libdino/src/service/message_processor.vala b/libdino/src/service/message_processor.vala
index d8a25da1..697eae4c 100644
--- a/libdino/src/service/message_processor.vala
+++ b/libdino/src/service/message_processor.vala
@@ -35,6 +35,7 @@ public class MessageProcessor : StreamInteractionModule, Object {
         received_pipeline.connect(new DeduplicateMessageListener(db));
         received_pipeline.connect(new StoreMessageListener(stream_interactor));
         received_pipeline.connect(new MamMessageListener(stream_interactor));
+        received_pipeline.connect(new SlackMessageListener());
     }
 
     public Entities.Message send_text(string text, Conversation conversation) {
@@ -73,7 +74,6 @@ public class MessageProcessor : StreamInteractionModule, Object {
         if (message_stanza.body == null) return;
 
         Entities.Message message = yield create_in_message(account, message_stanza);
-        if (message == null) return;
 
         Conversation? conversation = stream_interactor.get_module(ConversationManager.IDENTITY).get_conversation_for_message(message);
         if (conversation != null) {
@@ -101,23 +101,6 @@ public class MessageProcessor : StreamInteractionModule, Object {
         new_message.ourpart = new_message.direction == Entities.Message.DIRECTION_SENT ? message.from : message.to;
         new_message.stanza = message;
 
-        // Slack non-standard behavior
-        if (account.domainpart.index_of("xmpp.slack.com") == account.domainpart.length - 14) {
-            if (new_message.counterpart.equals_bare(account.bare_jid)) {
-                // Ignore messages from us, because we neither know which conversation they belong to, nor can match
-                // them to one of our send messages because of timestamp mismatches.
-                return null;
-            }
-            if (new_message.direction == Entities.Message.DIRECTION_RECEIVED && message.type_ == "chat" && new_message.body.index_of("["+account.localpart+"] ") == 0) {
-                // That is the best thing we can do, although allowing for attacks.
-                new_message.direction = Entities.Message.DIRECTION_SENT;
-                new_message.body = new_message.body.substring(account.localpart.length + 3);
-            }
-            if (message.stanza.get_attribute("ts") != null) {
-                new_message.time = new DateTime.from_unix_utc((int64) double.parse(message.stanza.get_attribute("ts")));
-            }
-        }
-
         Xep.MessageArchiveManagement.MessageFlag? mam_message_flag = Xep.MessageArchiveManagement.MessageFlag.get_flag(message);
         if (mam_message_flag != null) new_message.local_time = mam_message_flag.server_time;
         if (new_message.local_time == null || new_message.local_time.compare(new DateTime.now_utc()) > 0) new_message.local_time = new DateTime.now_utc();
@@ -229,6 +212,34 @@ public class MessageProcessor : StreamInteractionModule, Object {
         }
     }
 
+    private class SlackMessageListener : MessageListener {
+
+        public string[] after_actions_const = new string[]{ "DEDUPLICATE" };
+        public override string action_group { get { return "SLACK"; } }
+        public override string[] after_actions { get { return after_actions_const; } }
+
+        public override async bool run(Entities.Message message, Xmpp.MessageStanza stanza, Conversation conversation) {
+            // Slack non-standard behavior
+            Account account = conversation.account;
+            if (account.domainpart.index_of("xmpp.slack.com") == account.domainpart.length - 14) {
+                if (message.counterpart.equals_bare(account.bare_jid)) {
+                    // Ignore messages from us, because we neither know which conversation they belong to, nor can match
+                    // them to one of our send messages because of timestamp mismatches.
+                    return true;
+                }
+                if (message.direction == Entities.Message.DIRECTION_RECEIVED && stanza.type_ == "chat" && message.body.index_of("["+account.localpart+"] ") == 0) {
+                    // That is the best thing we can do, although allowing for attacks.
+                    message.direction = Entities.Message.DIRECTION_SENT;
+                    message.body = message.body.substring(account.localpart.length + 3);
+                }
+                if (stanza.stanza.get_attribute("ts") != null) {
+                    message.time = new DateTime.from_unix_utc((int64) double.parse(stanza.stanza.get_attribute("ts")));
+                }
+            }
+            return false;
+        }
+    }
+
     public Entities.Message create_out_message(string text, Conversation conversation) {
         Entities.Message message = new Entities.Message(text);
         message.type_ = Util.get_message_type_for_conversation(conversation);
diff --git a/xmpp-vala/tests/stanza.vala b/xmpp-vala/tests/stanza.vala
index 40b54a38..13fc626f 100644
--- a/xmpp-vala/tests/stanza.vala
+++ b/xmpp-vala/tests/stanza.vala
@@ -1,5 +1,3 @@
-using Xmpp.Core;
-
 namespace Xmpp.Test {
 
 class StanzaTest : Gee.TestCase {