diff --git a/elasticsearch/x-pack/shield/src/main/java/org/elasticsearch/shield/crypto/tool/SystemKeyTool.java b/elasticsearch/x-pack/shield/src/main/java/org/elasticsearch/shield/crypto/tool/SystemKeyTool.java
index decf56baf24..39ae9cdc9e2 100644
--- a/elasticsearch/x-pack/shield/src/main/java/org/elasticsearch/shield/crypto/tool/SystemKeyTool.java
+++ b/elasticsearch/x-pack/shield/src/main/java/org/elasticsearch/shield/crypto/tool/SystemKeyTool.java
@@ -22,6 +22,7 @@ import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
 import java.nio.file.attribute.PosixFileAttributeView;
 import java.nio.file.attribute.PosixFilePermission;
+import java.util.Locale;
 import java.util.Set;
 
 import static org.elasticsearch.common.cli.CliToolConfig.Builder.cmd;
@@ -97,10 +98,10 @@ public class SystemKeyTool extends CliTool {
                 }
                 terminal.println(Terminal.Verbosity.VERBOSE, "generating...");
                 byte[] key = InternalCryptoService.generateKey();
-                terminal.println(String.format("Storing generated key in [%s]...", path.toAbsolutePath()));
+                terminal.println(String.format(Locale.ROOT, "Storing generated key in [%s]...", path.toAbsolutePath()));
                 Files.write(path, key, StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING);
             } catch (IOException ioe) {
-                terminal.printError(String.format("Cannot generate and save system key file [%s]", path.toAbsolutePath()));
+                terminal.printError(String.format(Locale.ROOT, "Cannot generate and save system key file [%s]", path.toAbsolutePath()));
                 return ExitStatus.IO_ERROR;
             }
 
@@ -109,7 +110,7 @@ public class SystemKeyTool extends CliTool {
                 try {
                     Files.setPosixFilePermissions(path, PERMISSION_OWNER_READ_WRITE);
                 } catch (IOException ioe) {
-                    terminal.printError(String.format("Cannot set owner read/write permissions to generated system key file [%s]", path.toAbsolutePath()));
+                    terminal.printError(String.format(Locale.ROOT, "Cannot set owner read/write permissions to generated system key file [%s]", path.toAbsolutePath()));
                     return ExitStatus.IO_ERROR;
                 }
                 terminal.println("Ensure the generated key can be read by the user that Elasticsearch runs as, permissions are set to owner read/write only");
diff --git a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/watcher/actions/email/service/ManualPublicSmtpServersTester.java b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/watcher/actions/email/service/ManualPublicSmtpServersTester.java
index 6a277cf1032..786ae049342 100644
--- a/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/watcher/actions/email/service/ManualPublicSmtpServersTester.java
+++ b/elasticsearch/x-pack/watcher/src/test/java/org/elasticsearch/watcher/actions/email/service/ManualPublicSmtpServersTester.java
@@ -18,6 +18,7 @@ import org.elasticsearch.watcher.support.secret.SecretService;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Collections;
+import java.util.Locale;
 
 @AwaitsFix(bugUrl = "https://github.com/elastic/x-plugins/issues/379")
 public class ManualPublicSmtpServersTester {
@@ -121,7 +122,7 @@ public class ManualPublicSmtpServersTester {
 
             EmailService.EmailSent sent = service.send(email, null, profile);
 
-            terminal.println(String.format("email sent via account [%s]", sent.account()));
+            terminal.println(String.format(Locale.ROOT, "email sent via account [%s]", sent.account()));
         } finally {
             service.stop();
         }