diff --git a/src/main/java/org/elasticsearch/search/fetch/FetchPhase.java b/src/main/java/org/elasticsearch/search/fetch/FetchPhase.java
index 9fe79497713..956cee1020b 100644
--- a/src/main/java/org/elasticsearch/search/fetch/FetchPhase.java
+++ b/src/main/java/org/elasticsearch/search/fetch/FetchPhase.java
@@ -19,6 +19,7 @@
 
 package org.elasticsearch.search.fetch;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import org.apache.lucene.index.LeafReaderContext;
 import org.apache.lucene.index.ReaderUtil;
@@ -27,6 +28,7 @@ import org.apache.lucene.search.Filter;
 import org.apache.lucene.util.BitDocIdSet;
 import org.apache.lucene.util.BitSet;
 import org.elasticsearch.ElasticsearchIllegalArgumentException;
+import org.elasticsearch.ElasticsearchIllegalStateException;
 import org.elasticsearch.ExceptionsHelper;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.collect.Tuple;
@@ -293,7 +295,16 @@ public class FetchPhase implements SearchPhase {
             List<Map<String, Object>> nestedParsedSource;
             SearchHit.NestedIdentity nested = nestedIdentity;
             do {
-                nestedParsedSource = (List<Map<String, Object>>) XContentMapValues.extractValue(nested.getField().string(), sourceAsMap);
+                Object extractedValue = XContentMapValues.extractValue(nested.getField().string(), sourceAsMap);
+                if (extractedValue instanceof List) {
+                    // nested field has an array value in the _source
+                    nestedParsedSource = (List<Map<String, Object>>) extractedValue;
+                } else if (extractedValue instanceof Map) {
+                    // nested field has an object value in the _source. This just means the nested field has just one inner object, which is valid, but uncommon.
+                    nestedParsedSource = ImmutableList.of((Map < String, Object >) extractedValue);
+                } else {
+                    throw new ElasticsearchIllegalStateException("extracted source isn't an object or an array");
+                }
                 sourceAsMap = nestedParsedSource.get(nested.getOffset());
                 nested = nested.getChild();
             } while (nested != null);
diff --git a/src/test/java/org/elasticsearch/search/innerhits/InnerHitsTests.java b/src/test/java/org/elasticsearch/search/innerhits/InnerHitsTests.java
index fd210adb499..2a710e9cd37 100644
--- a/src/test/java/org/elasticsearch/search/innerhits/InnerHitsTests.java
+++ b/src/test/java/org/elasticsearch/search/innerhits/InnerHitsTests.java
@@ -645,4 +645,29 @@ public class InnerHitsTests extends ElasticsearchIntegrationTest {
         assertThat(innerHits.getAt(0).getNestedIdentity().getChild().getOffset(), equalTo(0));
     }
 
+    @Test
+    // https://github.com/elasticsearch/elasticsearch/issues/9723
+    public void testNestedDefinedAsObject() throws Exception {
+        assertAcked(prepareCreate("articles").addMapping("article", "comments", "type=nested", "title", "type=string"));
+
+        List<IndexRequestBuilder> requests = new ArrayList<>();
+        requests.add(client().prepareIndex("articles", "article", "1").setSource(jsonBuilder().startObject()
+                .field("title", "quick brown fox")
+                .startObject("comments").field("message", "fox eat quick").endObject()
+                .endObject()));
+        indexRandom(true, requests);
+
+        SearchResponse response = client().prepareSearch("articles")
+                .setQuery(nestedQuery("comments", matchQuery("comments.message", "fox")).innerHit(new QueryInnerHitBuilder()))
+                .get();
+        assertNoFailures(response);
+        assertHitCount(response, 1);
+        assertThat(response.getHits().getAt(0).id(), equalTo("1"));
+        assertThat(response.getHits().getAt(0).getInnerHits().get("comments").getTotalHits(), equalTo(1l));
+        assertThat(response.getHits().getAt(0).getInnerHits().get("comments").getAt(0).id(), equalTo("1"));
+        assertThat(response.getHits().getAt(0).getInnerHits().get("comments").getAt(0).getNestedIdentity().getField().string(), equalTo("comments"));
+        assertThat(response.getHits().getAt(0).getInnerHits().get("comments").getAt(0).getNestedIdentity().getOffset(), equalTo(0));
+        assertThat(response.getHits().getAt(0).getInnerHits().get("comments").getAt(0).getNestedIdentity().getChild(), nullValue());
+    }
+
 }