diff --git a/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/echo/ConfiguredEchoSocket.java b/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/echo/ConfiguredEchoSocket.java
index 8ec623aba4e..85d99856777 100644
--- a/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/echo/ConfiguredEchoSocket.java
+++ b/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/echo/ConfiguredEchoSocket.java
@@ -23,6 +23,7 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 import java.util.Objects;
 
 import javax.websocket.EndpointConfig;
@@ -67,9 +68,9 @@ public class ConfiguredEchoSocket
         switch (msg)
         {
             case "text-max":
-                return String.format("%,d",session.getMaxTextMessageBufferSize());
+                return String.format(Locale.US, "%,d",session.getMaxTextMessageBufferSize());
             case "binary-max":
-                return String.format("%,d",session.getMaxBinaryMessageBufferSize());
+                return String.format(Locale.US, "%,d",session.getMaxBinaryMessageBufferSize());
             case "decoders":
                 return join(config.getDecoders(),", ");
             case "encoders":
diff --git a/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/DoubleObjectTextSocket.java b/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/DoubleObjectTextSocket.java
index baa429977c4..eade593f5a8 100644
--- a/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/DoubleObjectTextSocket.java
+++ b/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/DoubleObjectTextSocket.java
@@ -19,6 +19,7 @@
 package org.eclipse.jetty.websocket.jsr356.server.samples.primitives;
 
 import java.io.IOException;
+import java.util.Locale;
 
 import javax.websocket.OnError;
 import javax.websocket.OnMessage;
@@ -52,7 +53,7 @@ public class DoubleObjectTextSocket
         }
         else
         {
-            String msg = String.format("%.4f",d);
+            String msg = String.format(Locale.US, "%.4f",d);
             session.getAsyncRemote().sendText(msg);
         }
     }
diff --git a/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/DoubleTextSocket.java b/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/DoubleTextSocket.java
index 43c712e03f6..71e5e4f154d 100644
--- a/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/DoubleTextSocket.java
+++ b/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/DoubleTextSocket.java
@@ -19,6 +19,7 @@
 package org.eclipse.jetty.websocket.jsr356.server.samples.primitives;
 
 import java.io.IOException;
+import java.util.Locale;
 
 import javax.websocket.OnError;
 import javax.websocket.OnMessage;
@@ -46,7 +47,7 @@ public class DoubleTextSocket
     @OnMessage
     public void onMessage(double d) throws IOException
     {
-        String msg = String.format("%.4f",d);
+        String msg = String.format(Locale.US, "%.4f",d);
         session.getAsyncRemote().sendText(msg);
     }
 
diff --git a/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/FloatObjectTextSocket.java b/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/FloatObjectTextSocket.java
index 2558daa70d0..db826226686 100644
--- a/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/FloatObjectTextSocket.java
+++ b/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/FloatObjectTextSocket.java
@@ -19,6 +19,7 @@
 package org.eclipse.jetty.websocket.jsr356.server.samples.primitives;
 
 import java.io.IOException;
+import java.util.Locale;
 
 import javax.websocket.OnError;
 import javax.websocket.OnMessage;
@@ -52,7 +53,7 @@ public class FloatObjectTextSocket
         }
         else
         {
-            String msg = String.format("%.4f",f);
+            String msg = String.format(Locale.US, "%.4f",f);
             session.getAsyncRemote().sendText(msg);
         }
     }
diff --git a/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/FloatTextSocket.java b/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/FloatTextSocket.java
index 1bb6cbefe8f..0b5423b2d12 100644
--- a/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/FloatTextSocket.java
+++ b/jetty-websocket/javax-websocket-server-impl/src/test/java/org/eclipse/jetty/websocket/jsr356/server/samples/primitives/FloatTextSocket.java
@@ -19,6 +19,7 @@
 package org.eclipse.jetty.websocket.jsr356.server.samples.primitives;
 
 import java.io.IOException;
+import java.util.Locale;
 
 import javax.websocket.OnError;
 import javax.websocket.OnMessage;
@@ -46,7 +47,7 @@ public class FloatTextSocket
     @OnMessage
     public void onMessage(float f) throws IOException
     {
-        String msg = String.format("%.4f",f);
+        String msg = String.format(Locale.US, "%.4f",f);
         session.getAsyncRemote().sendText(msg);
     }