diff --git a/build-logic/src/main/kotlin/polaris-java.gradle.kts b/build-logic/src/main/kotlin/polaris-java.gradle.kts
index e3b1767078..5ac9909720 100644
--- a/build-logic/src/main/kotlin/polaris-java.gradle.kts
+++ b/build-logic/src/main/kotlin/polaris-java.gradle.kts
@@ -137,7 +137,14 @@ dependencies {
   )
 }
 
-tasks.withType(Jar::class).configureEach {
+tasks.withType<Test>().configureEach {
+  systemProperty("file.encoding", "UTF-8")
+  systemProperty("user.language", "en")
+  systemProperty("user.country", "US")
+  systemProperty("user.variant", "")
+}
+
+tasks.withType<Jar>().configureEach {
   manifest {
     attributes(
       // Do not add any (more or less) dynamic information to jars, because that makes Gradle's
diff --git a/getting-started/spark/notebooks/Dockerfile b/getting-started/spark/notebooks/Dockerfile
index bcf45dbac3..fbec148b09 100644
--- a/getting-started/spark/notebooks/Dockerfile
+++ b/getting-started/spark/notebooks/Dockerfile
@@ -19,6 +19,8 @@
 
 FROM jupyter/all-spark-notebook:spark-3.5.0
 
+ENV LANGUAGE='en_US:en'
+
 COPY --chown=jovyan client /home/jovyan/client
 COPY --chown=jovyan regtests/requirements.txt /tmp
 RUN pip install -r /tmp/requirements.txt && \
diff --git a/quarkus/defaults/src/main/resources/application.properties b/quarkus/defaults/src/main/resources/application.properties
index fcfbc676ff..0cd79eadae 100644
--- a/quarkus/defaults/src/main/resources/application.properties
+++ b/quarkus/defaults/src/main/resources/application.properties
@@ -159,3 +159,7 @@ quarkus.index-dependency.guava.group-id=com.google.guava
 quarkus.index-dependency.guava.artifact-id=guava
 quarkus.index-dependency.protobuf.group-id=com.google.protobuf
 quarkus.index-dependency.protobuf.artifact-id=protobuf-java
+
+# force the locale, just in case the system's using another default locale
+quarkus.default-locale=en_US
+
diff --git a/regtests/Dockerfile b/regtests/Dockerfile
index c41e6dcdb4..fd21b02ece 100644
--- a/regtests/Dockerfile
+++ b/regtests/Dockerfile
@@ -21,6 +21,7 @@ FROM docker.io/apache/spark:3.5.5-java17-python3
 ARG POLARIS_HOST=polaris
 ENV POLARIS_HOST=$POLARIS_HOST
 ENV SPARK_HOME=/opt/spark
+ENV LANGUAGE='en_US:en'
 
 USER root
 RUN apt update
diff --git a/site/docker/Dockerfile b/site/docker/Dockerfile
index 98a6aad1c8..714b1ccf53 100644
--- a/site/docker/Dockerfile
+++ b/site/docker/Dockerfile
@@ -19,6 +19,8 @@
 
 FROM ubuntu:24.04 AS hugo
 
+ENV LANGUAGE='en_US:en'
+
 RUN apt-get update
 RUN apt-get install --yes golang hugo asciidoctor npm curl
 RUN apt-get clean