diff --git a/Netdisco/Changes b/Netdisco/Changes
index 1349b861..4ff7e67f 100644
--- a/Netdisco/Changes
+++ b/Netdisco/Changes
@@ -8,6 +8,7 @@
 
   * [#255] undefined host error in netdisco-do psql
   * [#250] Linux SSHColletor cannot handle uppercase MACs
+  * Return from device discover if device is unknown
 
 2.033004 - 2015-11-16
 
diff --git a/Netdisco/lib/App/Netdisco/Daemon/Worker/Poller/Device.pm b/Netdisco/lib/App/Netdisco/Daemon/Worker/Poller/Device.pm
index fb4c5efd..23950bff 100644
--- a/Netdisco/lib/App/Netdisco/Daemon/Worker/Poller/Device.pm
+++ b/Netdisco/lib/App/Netdisco/Daemon/Worker/Poller/Device.pm
@@ -40,7 +40,9 @@ sub discover {
   my ($self, $job) = @_;
 
   my $device = get_device($job->device)
-    or job_error("discover failed: unable to interpret device parameter");
+    or return job_error(
+      "discover failed: unable to interpret device parameter: "
+      . ($job->device || "''"));
   my $host = $device->ip;
 
   if ($device->ip eq '0.0.0.0') {