diff --git a/lib/functions.sh b/lib/functions.sh
index 3fcae38..9f3a43f 100644
--- a/lib/functions.sh
+++ b/lib/functions.sh
@@ -116,7 +116,7 @@ assertVarsNotEmpty() {
 	MISSING_VARS=""
 
 	for VAR in $@; do
-	if [ -z "${!VAR}" ]; then
+		if [ -z "${VAR+x}" ] || [ -z "$VAR" ]; then
 			MISSING_VARS+="$VAR "
 		fi
 	done