diff --git a/src/lib/Hydra/Controller/Build.pm b/src/lib/Hydra/Controller/Build.pm
index e94f9d9c..411065d3 100644
--- a/src/lib/Hydra/Controller/Build.pm
+++ b/src/lib/Hydra/Controller/Build.pm
@@ -1,5 +1,6 @@
 package Hydra::Controller::Build;
 
+use utf8;
 use strict;
 use warnings;
 use base 'Hydra::Base::Controller::NixChannel';
@@ -18,6 +19,8 @@ use Encode;
 sub buildChain :Chained('/') :PathPart('build') :CaptureArgs(1) {
     my ($self, $c, $id) = @_;
 
+    $id =~ /^[0-9]+$/ or error($c, "Invalid build ID ‘$id’.");
+
     $c->stash->{id} = $id;
 
     $c->stash->{build} = getBuild($c, $id);