diff --git a/docs-core/src/main/java/com/sismics/docs/core/constant/Constants.java b/docs-core/src/main/java/com/sismics/docs/core/constant/Constants.java
index 30312918..7309c0af 100644
--- a/docs-core/src/main/java/com/sismics/docs/core/constant/Constants.java
+++ b/docs-core/src/main/java/com/sismics/docs/core/constant/Constants.java
@@ -48,5 +48,5 @@ public class Constants {
     /**
      * Supported document languages.
      */
-    public static final List<String> SUPPORTED_LANGUAGES = Lists.newArrayList("eng", "fra");
+    public static final List<String> SUPPORTED_LANGUAGES = Lists.newArrayList("eng", "fra", "jpn");
 }
diff --git a/docs-core/src/main/java/com/sismics/docs/core/dao/lucene/LuceneDao.java b/docs-core/src/main/java/com/sismics/docs/core/dao/lucene/LuceneDao.java
index 6b5a72a9..466728bb 100644
--- a/docs-core/src/main/java/com/sismics/docs/core/dao/lucene/LuceneDao.java
+++ b/docs-core/src/main/java/com/sismics/docs/core/dao/lucene/LuceneDao.java
@@ -1,7 +1,9 @@
 package com.sismics.docs.core.dao.lucene;
 
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Set;
 
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.StringField;
@@ -100,7 +102,7 @@ public class LuceneDao {
      * @return List of file IDs
      * @throws Exception
      */
-    public List<String> search(String userId, String searchQuery, int limit) throws Exception {
+    public Set<String> search(String userId, String searchQuery, int limit) throws Exception {
         // Escape query and add quotes so QueryParser generate a PhraseQuery
         searchQuery = "\"" + QueryParserUtil.escape(searchQuery) + "\"";
         
@@ -125,7 +127,7 @@ public class LuceneDao {
         ScoreDoc[] docs = topDocs.scoreDocs;
         
         // Extract file IDs
-        List<String> fileIdList = new ArrayList<String>();
+        Set<String> fileIdList = new HashSet<String>();
         for (int i = 0; i < docs.length; i++) {
             String id = searcher.doc(docs[i].doc).get("id");
             fileIdList.add(id);
diff --git a/docs-web/src/main/webapp/img/flag/jpn.png b/docs-web/src/main/webapp/img/flag/jpn.png
new file mode 100644
index 00000000..325fbad3
Binary files /dev/null and b/docs-web/src/main/webapp/img/flag/jpn.png differ
diff --git a/docs-web/src/main/webapp/partial/docs/document.edit.html b/docs-web/src/main/webapp/partial/docs/document.edit.html
index ea83944c..2077ac42 100644
--- a/docs-web/src/main/webapp/partial/docs/document.edit.html
+++ b/docs-web/src/main/webapp/partial/docs/document.edit.html
@@ -26,6 +26,7 @@
       <select id="inputLanguage" ng-model="document.language">
         <option value="fra">French</option>
         <option value="eng">English</option>
+        <option value="jpn">Japanese</option>
       </select>
     </div>
   </div>