diff --git a/arpspoof/rootfs/etc/cont-init.d/99-run.sh b/arpspoof/rootfs/etc/cont-init.d/99-run.sh
index 4c633a894..b44992d0f 100644
--- a/arpspoof/rootfs/etc/cont-init.d/99-run.sh
+++ b/arpspoof/rootfs/etc/cont-init.d/99-run.sh
@@ -1,6 +1,9 @@
 #!/usr/bin/env bashio
 # shellcheck shell=bash
 
+# Avoid unbound variables
+set +u
+
 # Autodefine if not defined
 if [ -n "$INTERFACE_NAME" ]; then
     # shellcheck disable=SC2155