diff --git a/server/src/main/java/org/elasticsearch/index/store/FsDirectoryFactory.java b/server/src/main/java/org/elasticsearch/index/store/FsDirectoryFactory.java
index 310f3de949527..67498a950fff2 100644
--- a/server/src/main/java/org/elasticsearch/index/store/FsDirectoryFactory.java
+++ b/server/src/main/java/org/elasticsearch/index/store/FsDirectoryFactory.java
@@ -159,6 +159,7 @@ boolean useDelegate(String name) {
                 case "tim":
                 case "tip":
                 case "cfs":
+                case "dim":
                     return true;
                 default:
                     return false;
diff --git a/server/src/test/java/org/elasticsearch/index/store/FsDirectoryFactoryTests.java b/server/src/test/java/org/elasticsearch/index/store/FsDirectoryFactoryTests.java
index dfba867bf3c1d..6bec760a5521a 100644
--- a/server/src/test/java/org/elasticsearch/index/store/FsDirectoryFactoryTests.java
+++ b/server/src/test/java/org/elasticsearch/index/store/FsDirectoryFactoryTests.java
@@ -63,6 +63,7 @@ public void testPreload() throws IOException {
             assertTrue(hybridDirectory.useDelegate("foo.tim"));
             assertTrue(hybridDirectory.useDelegate("foo.tip"));
             assertTrue(hybridDirectory.useDelegate("foo.cfs"));
+            assertTrue(hybridDirectory.useDelegate("foo.dim"));
             assertFalse(hybridDirectory.useDelegate("foo.bar"));
             MMapDirectory delegate = hybridDirectory.getDelegate();
             assertThat(delegate, Matchers.instanceOf(FsDirectoryFactory.PreLoadMMapDirectory.class));