diff --git a/test/Dockerfile-centos7 b/test/Dockerfile-centos7
index 794e0bd..56dff7d 100644
--- a/test/Dockerfile-centos7
+++ b/test/Dockerfile-centos7
@@ -7,6 +7,11 @@ RUN yum -y install git curl ldns bind-utils wget which nginx
 RUN yum -y install ftp vsftpd
 RUN yum -y install openssh-server
 
+# Set locale
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
+
 WORKDIR /root
 RUN mkdir -p /etc/nginx/pki/private
 COPY ./test/test-config/nginx-ubuntu-no-ssl /etc/nginx/conf.d/default.conf
diff --git a/test/Dockerfile-centos7-duckdns b/test/Dockerfile-centos7-duckdns
index bf85592..be26c79 100644
--- a/test/Dockerfile-centos7-duckdns
+++ b/test/Dockerfile-centos7-duckdns
@@ -7,6 +7,11 @@ RUN yum -y update
 RUN yum -y install epel-release
 RUN yum -y install git curl bind-utils ldns wget which nginx
 
+# Set locale
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
+
 ENV staging "true"
 ENV dynamic_dns "dynu"
 ENV DUCKDNS_TOKEN 1d616aa9-b8e4-4bb4-b312-3289de82badb
diff --git a/test/Dockerfile-centos7-dynu b/test/Dockerfile-centos7-dynu
index 01d41a7..65c8051 100644
--- a/test/Dockerfile-centos7-dynu
+++ b/test/Dockerfile-centos7-dynu
@@ -7,6 +7,11 @@ RUN yum -y update
 RUN yum -y install epel-release
 RUN yum -y install git curl bind-utils ldns wget which nginx
 
+# Set locale
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
+
 ENV staging "true"
 ENV dynamic_dns "duckdns"
 ENV DYNU_API_KEY 65cXefd35XbYf36546eg5dYcZT6X52Y2
diff --git a/test/Dockerfile-centos8 b/test/Dockerfile-centos8
index 210bd8e..4ac3114 100644
--- a/test/Dockerfile-centos8
+++ b/test/Dockerfile-centos8
@@ -1,6 +1,6 @@
 FROM centos:centos8
 
-# Note this image uses drill, does not have dig or nslookup installed
+# Note this image does not have drill
 
 # Update and install required software
 RUN yum -y update
@@ -9,6 +9,11 @@ RUN yum -y install git curl bind-utils wget which nginx
 RUN yum -y install ftp vsftpd
 RUN yum -y install openssh-server
 
+# Set locale
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
+
 WORKDIR /root
 RUN mkdir -p /etc/nginx/pki/private
 COPY ./test/test-config/nginx-ubuntu-no-ssl /etc/nginx/conf.d/default.conf
diff --git a/test/Dockerfile-debian b/test/Dockerfile-debian
index 04e5232..1a57107 100644
--- a/test/Dockerfile-debian
+++ b/test/Dockerfile-debian
@@ -7,6 +7,13 @@ RUN apt-get update --fix-missing
 RUN apt-get install -y git curl dnsutils ldnsutils wget nginx-light
 RUN apt-get install -y ftp vsftpd
 RUN apt-get install -y openssh-server
+RUN apt-get install -y locales # for idn testing
+
+# Set locale
+RUN sed -i '/en_US.UTF-8/s/^# //g' /etc/locale.gen && locale-gen
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
 
 WORKDIR /root
 RUN mkdir -p /etc/nginx/pki/private
diff --git a/test/Dockerfile-ubuntu b/test/Dockerfile-ubuntu
index dd8338d..5dee554 100644
--- a/test/Dockerfile-ubuntu
+++ b/test/Dockerfile-ubuntu
@@ -11,6 +11,13 @@ RUN apt-get install -y git curl dnsutils ldnsutils wget nginx-light
 RUN apt-get install -y vim dos2unix # for debugging
 RUN apt-get install -y ftp vsftpd
 RUN apt-get install -y openssh-server
+RUN apt-get install -y locales # for idn testing
+
+# Set locale
+RUN sed -i '/en_US.UTF-8/s/^# //g' /etc/locale.gen && locale-gen
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
 
 # Setup ftp
 ENV VSFTPD_CONF=/etc/vsftpd.conf
diff --git a/test/Dockerfile-ubuntu-duckdns b/test/Dockerfile-ubuntu-duckdns
index a07bb23..f0f2edd 100644
--- a/test/Dockerfile-ubuntu-duckdns
+++ b/test/Dockerfile-ubuntu-duckdns
@@ -14,6 +14,13 @@ ENV DUCKDNS_TOKEN 1d616aa9-b8e4-4bb4-b312-3289de82badb
 RUN apt-get update --fix-missing
 RUN apt-get install -y git curl dnsutils ldnsutils wget nginx-light
 RUN apt-get install -y vim dos2unix # for debugging
+RUN apt-get install -y locales # for idn testing
+
+# Set locale
+RUN sed -i '/en_US.UTF-8/s/^# //g' /etc/locale.gen && locale-gen
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
 
 WORKDIR /root
 
diff --git a/test/Dockerfile-ubuntu-dynu b/test/Dockerfile-ubuntu-dynu
index 2ea8c31..b010293 100644
--- a/test/Dockerfile-ubuntu-dynu
+++ b/test/Dockerfile-ubuntu-dynu
@@ -14,6 +14,13 @@ ENV DYNU_API_KEY 65cXefd35XbYf36546eg5dYcZT6X52Y2
 RUN apt-get update --fix-missing
 RUN apt-get install -y git curl dnsutils ldnsutils wget nginx-light
 RUN apt-get install -y vim dos2unix # for debugging
+RUN apt-get install -y locales # for idn testing
+
+# Set locale
+RUN sed -i '/en_US.UTF-8/s/^# //g' /etc/locale.gen && locale-gen
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
 
 WORKDIR /root
 
diff --git a/test/Dockerfile-ubuntu16 b/test/Dockerfile-ubuntu16
index 00a4589..8e4ecae 100644
--- a/test/Dockerfile-ubuntu16
+++ b/test/Dockerfile-ubuntu16
@@ -8,6 +8,13 @@ RUN apt-get update --fix-missing
 RUN apt-get install -y git curl dnsutils ldnsutils wget nginx-light
 RUN apt-get install -y ftp vsftpd
 RUN apt-get install -y openssh-server
+RUN apt-get install -y locales # for idn testing
+
+# Set locale
+RUN sed -i '/en_US.UTF-8/s/^# //g' /etc/locale.gen && locale-gen
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
 
 WORKDIR /root
 RUN mkdir -p /etc/nginx/pki/private
diff --git a/test/Dockerfile-ubuntu18 b/test/Dockerfile-ubuntu18
index 91a0429..98b62d5 100644
--- a/test/Dockerfile-ubuntu18
+++ b/test/Dockerfile-ubuntu18
@@ -8,6 +8,13 @@ RUN apt-get update --fix-missing
 RUN apt-get install -y git curl dnsutils ldnsutils wget gawk nginx-light
 RUN apt-get install -y ftp vsftpd
 RUN apt-get install -y openssh-server
+RUN apt-get install -y locales # for idn testing
+
+# Set locale
+RUN sed -i '/en_US.UTF-8/s/^# //g' /etc/locale.gen && locale-gen
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8
 
 WORKDIR /root
 RUN mkdir -p /etc/nginx/pki/private