diff --git a/core/src/main/java/org/elasticsearch/index/mapper/ip/IpFieldMapper.java b/core/src/main/java/org/elasticsearch/index/mapper/ip/IpFieldMapper.java
index 5f5a3d85fe1..0d9810bd405 100644
--- a/core/src/main/java/org/elasticsearch/index/mapper/ip/IpFieldMapper.java
+++ b/core/src/main/java/org/elasticsearch/index/mapper/ip/IpFieldMapper.java
@@ -396,7 +396,11 @@ public class IpFieldMapper extends FieldMapper implements AllFieldMapper.Include
         super.doXContentBody(builder, includeDefaults, params);
 
         if (includeDefaults || fieldType().nullValue() != null) {
-            builder.field("null_value", InetAddresses.toAddrString((InetAddress) fieldType().nullValue()));
+            Object nullValue = fieldType().nullValue();
+            if (nullValue != null) {
+                nullValue = InetAddresses.toAddrString((InetAddress) nullValue);
+            }
+            builder.field("null_value", nullValue);
         }
 
         if (includeDefaults || ignoreMalformed.explicit()) {
diff --git a/core/src/test/java/org/elasticsearch/index/mapper/ip/IpFieldMapperTests.java b/core/src/test/java/org/elasticsearch/index/mapper/ip/IpFieldMapperTests.java
index 25979c5a632..d99b37fc667 100644
--- a/core/src/test/java/org/elasticsearch/index/mapper/ip/IpFieldMapperTests.java
+++ b/core/src/test/java/org/elasticsearch/index/mapper/ip/IpFieldMapperTests.java
@@ -25,6 +25,8 @@ import org.apache.lucene.index.IndexableField;
 import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.common.compress.CompressedXContent;
 import org.elasticsearch.common.network.InetAddresses;
+import org.elasticsearch.common.xcontent.ToXContent;
+import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentFactory;
 import org.elasticsearch.index.IndexService;
 import org.elasticsearch.index.mapper.DocumentMapper;
@@ -269,4 +271,22 @@ public class IpFieldMapperTests extends ESSingleNodeTestCase {
         assertEquals(new BytesRef(InetAddressPoint.encode(InetAddresses.forString("::1"))), dvField.binaryValue());
         assertFalse(dvField.fieldType().stored());
     }
+
+    public void testSerializeDefaults() throws Exception {
+        String mapping = XContentFactory.jsonBuilder().startObject().startObject("type")
+            .startObject("properties").startObject("field").field("type", "ip").endObject().endObject()
+            .endObject().endObject().string();
+
+        DocumentMapper docMapper = parser.parse("type", new CompressedXContent(mapping));
+        IpFieldMapper mapper = (IpFieldMapper)docMapper.root().getMapper("field");
+        XContentBuilder builder = XContentFactory.jsonBuilder().startObject();
+        mapper.doXContentBody(builder, true, ToXContent.EMPTY_PARAMS);
+        String got = builder.endObject().string();
+
+        // it would be nice to check the entire serialized default mapper, but there are
+        // a whole lot of bogus settings right now it picks up from calling super.doXContentBody...
+        assertTrue(got, got.contains("\"null_value\":null"));
+        assertTrue(got, got.contains("\"ignore_malformed\":false"));
+        assertTrue(got, got.contains("\"include_in_all\":false"));
+    }
 }