diff --git a/pyaptly/publish.py b/pyaptly/publish.py
index 8f914af..bb18a83 100644
--- a/pyaptly/publish.py
+++ b/pyaptly/publish.py
@@ -85,7 +85,12 @@ def publish_cmd_update(cfg, publish_name, publish_config, ignore_existing=False)
         return cmd
 
     publish_fullname = "%s %s" % (publish_name, publish_config["distribution"])
-    current_snapshots = state_reader.state_reader().publish_map()[publish_fullname]
+    # TODO: add flag --create to create publishes when they haven't been created yet
+    # TODO: Fail gracefully and show an error when there is no existing publish
+    try:
+        current_snapshots = state_reader.state_reader().publish_map()[publish_fullname]
+    except KeyError as e:
+        util.exit_with_error("The publish hasn't been created yet: " + e)
     if "snapshots" in publish_config:
         snapshots_config = publish_config["snapshots"]
         new_snapshots = [
@@ -129,13 +134,15 @@ def publish_cmd_update(cfg, publish_name, publish_config, ignore_existing=False)
                     continue
                 prefix_to_search = re.sub("%T$", "", snap["name"])
 
-                current_snapshot = [
-                    snap_name
-                    for snap_name in sorted(current_snapshots, key=lambda x: -len(x))
-                    if snap_name.startswith(prefix_to_search)
-                ][0]
-
-                snapshot.clone_snapshot(current_snapshot, archive).execute()
+                current_snapshot = None
+                for snap_name in sorted(current_snapshots, key=lambda x: -len(x)):
+                    if snap_name.startswith(prefix_to_search):
+                        current_snapshot = snap_name
+                        break
+                if current_snapshot is None:
+                    lg.warn("Snapshot %s doesn't exist on to-be archived publish %s." % (snap["name"], publish_fullname))
+                else:
+                    snapshot.clone_snapshot(current_snapshot, archive).execute()
 
     publish_cmd.append("switch")
     options.append("-component=%s" % ",".join(components))