diff --git a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequest.java b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequest.java
index 926ae175d65..68687081453 100644
--- a/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequest.java
+++ b/server/src/main/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequest.java
@@ -254,7 +254,7 @@ public class PutMappingRequest extends AcknowledgedRequest<PutMappingRequest> im
      * The mapping source definition.
      */
     public PutMappingRequest source(XContentBuilder mappingBuilder) {
-        return source(Strings.toString(mappingBuilder), mappingBuilder.contentType());
+        return source(BytesReference.bytes(mappingBuilder), mappingBuilder.contentType());
     }
 
     /**
@@ -264,7 +264,7 @@ public class PutMappingRequest extends AcknowledgedRequest<PutMappingRequest> im
         try {
             XContentBuilder builder = XContentFactory.contentBuilder(XContentType.JSON);
             builder.map(mappingSource);
-            return source(Strings.toString(builder), XContentType.JSON);
+            return source(BytesReference.bytes(builder), builder.contentType());
         } catch (IOException e) {
             throw new ElasticsearchGenerationException("Failed to generate [" + mappingSource + "]", e);
         }
diff --git a/server/src/test/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequestTests.java b/server/src/test/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequestTests.java
index 6fddf2dd5f8..593cdc60e8a 100644
--- a/server/src/test/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequestTests.java
+++ b/server/src/test/java/org/elasticsearch/action/admin/indices/mapping/put/PutMappingRequestTests.java
@@ -23,7 +23,6 @@ import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.xcontent.XContentBuilder;
-import org.elasticsearch.common.xcontent.XContentFactory;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.common.xcontent.XContentType;
 import org.elasticsearch.common.xcontent.json.JsonXContent;
@@ -135,20 +134,8 @@ public class PutMappingRequestTests extends ESTestCase {
 
         String type = randomAlphaOfLength(5);
         request.type(type);
-        request.source(randomMapping());
+        request.source(RandomCreateIndexGenerator.randomMapping());
 
         return request;
     }
-
-    private static XContentBuilder randomMapping() throws IOException {
-        XContentBuilder builder = XContentFactory.jsonBuilder();
-        builder.startObject();
-
-        if (randomBoolean()) {
-            RandomCreateIndexGenerator.randomMappingFields(builder, true);
-        }
-
-        builder.endObject();
-        return builder;
-    }
 }