diff --git a/roles/edulive/templates/livebuilder.sh b/roles/edulive/templates/livebuilder.sh
index d8ef679..92f7aab 100644
--- a/roles/edulive/templates/livebuilder.sh
+++ b/roles/edulive/templates/livebuilder.sh
@@ -21,6 +21,11 @@ run_build(){
 
 ## main:
 
+if ! auto-apt-proxy | grep -q 'http://127.0.0.1:3142' ; then
+    echo "Cannot find the local apt proxy needed to build live images."
+    exit 1
+fi
+
 for IMG in {{ build_images|join(' ') }} ; do
     echo "=========== Building image $IMG ==========="
     run_build $IMG