diff --git a/test/hotspot/jtreg/containers/docker/TestJcmd.java b/test/hotspot/jtreg/containers/docker/TestJcmd.java
index 3cfe2945e92..fcd5c665f2b 100644
--- a/test/hotspot/jtreg/containers/docker/TestJcmd.java
+++ b/test/hotspot/jtreg/containers/docker/TestJcmd.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -143,6 +143,7 @@ public class TestJcmd {
         sb.append(String.format("FROM %s:%s\n", DockerfileConfig.getBaseImageName(),
                                 DockerfileConfig.getBaseImageVersion()));
         sb.append("COPY /jdk /jdk\n");
+        sb.append("ENV LANG=C.UTF-8\n");
         sb.append("ENV JAVA_HOME=/jdk\n");
 
         if (!IS_PODMAN) { // only needed for docker
diff --git a/test/jdk/jdk/internal/platform/docker/TestDockerMemoryMetricsSubgroup.java b/test/jdk/jdk/internal/platform/docker/TestDockerMemoryMetricsSubgroup.java
index 7d5dbca6f7c..4b487934169 100644
--- a/test/jdk/jdk/internal/platform/docker/TestDockerMemoryMetricsSubgroup.java
+++ b/test/jdk/jdk/internal/platform/docker/TestDockerMemoryMetricsSubgroup.java
@@ -91,7 +91,8 @@ public class TestDockerMemoryMetricsSubgroup {
             .addDockerOpts("--volume", Utils.TEST_JDK + ":/jdk")
             .addDockerOpts("--privileged")
             .addDockerOpts("--cgroupns=" + (privateNamespace ? "private" : "host"))
-            .addDockerOpts("--memory", outerGroupMemorySize);
+            .addDockerOpts("--memory", outerGroupMemorySize)
+            .addDockerOpts("-e", "LANG=C.UTF-8");
         opts.addClassOptions("mkdir -p /sys/fs/cgroup/memory/test ; " +
             "echo " + innerSize + " > /sys/fs/cgroup/memory/test/memory.limit_in_bytes ; " +
             "echo $$ > /sys/fs/cgroup/memory/test/cgroup.procs ; " +
@@ -112,6 +113,7 @@ public class TestDockerMemoryMetricsSubgroup {
             .addDockerOpts("--volume", Utils.TEST_JDK + ":/jdk")
             .addDockerOpts("--privileged")
             .addDockerOpts("--cgroupns=" + (privateNamespace ? "private" : "host"))
+            .addDockerOpts("-e", "LANG=C.UTF-8")
             .addDockerOpts("--memory", outerGroupMemorySize);
         opts.addClassOptions("mkdir -p /sys/fs/cgroup/memory/test ; " +
             "echo $$ > /sys/fs/cgroup/memory/test/cgroup.procs ; " +
diff --git a/test/lib/jdk/test/lib/containers/docker/DockerTestUtils.java b/test/lib/jdk/test/lib/containers/docker/DockerTestUtils.java
index b013561be0b..bd9a706e3a4 100644
--- a/test/lib/jdk/test/lib/containers/docker/DockerTestUtils.java
+++ b/test/lib/jdk/test/lib/containers/docker/DockerTestUtils.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -380,6 +380,7 @@ public class DockerTestUtils {
         }
         template = template + "COPY /jdk /jdk\n" +
             "ENV JAVA_HOME=/jdk\n" +
+            "ENV LANG=C.UTF-8\n" +
             "CMD [\"/bin/bash\"]\n";
         String dockerFileStr = String.format(template, baseImage, baseImageVersion);
         Files.writeString(dockerfile, dockerFileStr);