diff --git a/docker-compose.yml b/docker-compose.yml
index 0ad69aa..a487551 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -1,7 +1,9 @@
 version: '3.0'
 services:
   api:
-    build: .
+    build:
+      context: .
+      dockerfile: dockerfile-amd64
     ports:
       - "5000:5000"
       - "5678:5678"
diff --git a/main.py b/main.py
index 5affc2d..13d89eb 100644
--- a/main.py
+++ b/main.py
@@ -20,7 +20,9 @@ def process(self, content):
             return
         if "event" in content and "files" in content["event"]:
             app.logger.info("Received event contains files")
-            # TODO: switch to manageable list of channel ids
+            if "image" not in content["event"]["files"][0]["mimetype"]:
+                app.logger.info("Received file is not an image")
+                return
             if content["event"]["channel"] in self.read_channels:
                 detector.detect(content["event"]["files"][0]["url_private_download"])
             else: