diff --git a/ci/helm_test.sh b/ci/helm_test.sh
index 9a7a4b6..9972ad2 100755
--- a/ci/helm_test.sh
+++ b/ci/helm_test.sh
@@ -10,7 +10,7 @@ fi
 
 
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
-POSTFIX=$(cat /dev/urandom | tr -dc 'a-zA-Z0-9' | fold -w 10 | head -n 1)
+POSTFIX=$(cat /dev/urandom | tr -dc 'a-z0-9' | fold -w 10 | head -n 1)
 NAMESPACE="covidok-ci-$POSTFIX"
 HELM_PACKAGE="covid-$POSTFIX"