diff --git a/src/plugins/elasticsearch/lib/create_kibana_index.js b/src/plugins/elasticsearch/lib/create_kibana_index.js
index d122ef4e3214c..b35e13fa84156 100644
--- a/src/plugins/elasticsearch/lib/create_kibana_index.js
+++ b/src/plugins/elasticsearch/lib/create_kibana_index.js
@@ -1,5 +1,7 @@
 import SetupError from './setup_error';
 import { format } from 'util';
+import { mappings } from './kibana_index_mappings';
+
 module.exports = function (server) {
   const client = server.plugins.elasticsearch.client;
   const index = server.config().get('kibana.index');
@@ -16,16 +18,7 @@ module.exports = function (server) {
       settings: {
         number_of_shards: 1
       },
-      mappings: {
-        config: {
-          properties: {
-            buildNum: {
-              type: 'string',
-              index: 'not_analyzed'
-            }
-          }
-        }
-      }
+      mappings
     }
   })
   .catch(handleError('Unable to create Kibana index "<%= kibana.index %>"'))
diff --git a/src/plugins/elasticsearch/lib/kibana_index_mappings.js b/src/plugins/elasticsearch/lib/kibana_index_mappings.js
new file mode 100644
index 0000000000000..0d0204aeeecb5
--- /dev/null
+++ b/src/plugins/elasticsearch/lib/kibana_index_mappings.js
@@ -0,0 +1,10 @@
+export const mappings = {
+  config: {
+    properties: {
+      buildNum: {
+        type: 'string',
+        index: 'not_analyzed'
+      }
+    }
+  }
+};
diff --git a/src/plugins/elasticsearch/lib/migrate_config.js b/src/plugins/elasticsearch/lib/migrate_config.js
index 0eba1e0621717..7b16990e21297 100644
--- a/src/plugins/elasticsearch/lib/migrate_config.js
+++ b/src/plugins/elasticsearch/lib/migrate_config.js
@@ -1,4 +1,5 @@
 import upgrade from './upgrade_config';
+import { mappings } from './kibana_index_mappings';
 
 module.exports = function (server) {
   const config = server.config();
@@ -8,11 +9,16 @@ module.exports = function (server) {
     type: 'config',
     body: {
       size: 1000,
-      sort: [ { buildNum: { order: 'desc', ignore_unmapped: true } } ]
+      sort: [
+        {
+          buildNum: {
+            order: 'desc',
+            unmapped_type: mappings.config.properties.buildNum.type
+          }
+        }
+      ]
     }
   };
 
   return client.search(options).then(upgrade(server));
 };
-
-