diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/alias/Alias.java b/server/src/main/java/org/elasticsearch/action/admin/indices/alias/Alias.java
index bd3c77cdb264a..9172500a8cb50 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/alias/Alias.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/alias/Alias.java
@@ -28,7 +28,8 @@
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.io.stream.Streamable;
 import org.elasticsearch.common.xcontent.ToXContent;
-import org.elasticsearch.common.xcontent.ToXContentObject;
+import org.elasticsearch.common.xcontent.ToXContent.Params;
+import org.elasticsearch.common.xcontent.ToXContentFragment;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentFactory;
 import org.elasticsearch.common.xcontent.XContentParser;
@@ -42,7 +43,7 @@
 /**
  * Represents an alias, to be associated with an index
  */
-public class Alias implements Streamable, ToXContentObject {
+public class Alias implements Streamable, ToXContentFragment {
 
     private static final ParseField FILTER = new ParseField("filter");
     private static final ParseField ROUTING = new ParseField("routing");
@@ -248,6 +249,11 @@ public XContentBuilder toXContent(XContentBuilder builder, Params params) throws
         return builder;
     }
 
+    @Override
+    public String toString() {
+        return Strings.toString(this);
+    }
+
     @Override
     public boolean equals(Object o) {
         if (this == o) return true;
diff --git a/server/src/test/java/org/elasticsearch/action/admin/indices/template/put/PutIndexTemplateRequestTests.java b/server/src/test/java/org/elasticsearch/action/admin/indices/template/put/PutIndexTemplateRequestTests.java
index 577a8b55e61a3..c21e6b3c225f0 100644
--- a/server/src/test/java/org/elasticsearch/action/admin/indices/template/put/PutIndexTemplateRequestTests.java
+++ b/server/src/test/java/org/elasticsearch/action/admin/indices/template/put/PutIndexTemplateRequestTests.java
@@ -150,7 +150,9 @@ protected PutIndexTemplateRequest createTestInstance() {
         request.patterns(Arrays.asList(generateRandomStringArray(20, 100, false, false)));
         int numAlias = between(0, 5);
         for (int i = 0; i < numAlias; i++) {
-            Alias alias = new Alias(randomRealisticUnicodeOfLengthBetween(1, 10));
+            // some ASCII or Latin-1 control characters, especially newline, can lead to
+            // problems with yaml parsers, that's why we filter them here (see #30911)
+            Alias alias = new Alias(randomRealisticUnicodeOfLengthBetween(1, 10).replaceAll("\\p{Cc}", ""));
             if (randomBoolean()) {
                 alias.indexRouting(randomRealisticUnicodeOfLengthBetween(1, 10));
             }