diff --git a/Makefile b/Makefile
index c4702db47..9e27db050 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 REPO?=quay.io/coreos/prometheus-operator
 TAG?=$(shell git rev-parse --short HEAD)
-NAMESPACE?=po-e2e-$(shell LC_CTYPE=C tr -dc a-z0-9 < /dev/urandom | head -c 13 ; echo '')
+NAMESPACE?=po-e2e-$(shell LC_ALL=C tr -dc a-z0-9 < /dev/urandom | head -c 13 ; echo '')
 KUBECONFIG?=$(HOME)/.kube/config
 
 PROMU := $(GOPATH)/bin/promu