diff --git a/docs-web/src/main/java/com/sismics/docs/rest/resource/TagResource.java b/docs-web/src/main/java/com/sismics/docs/rest/resource/TagResource.java
index 27efc454..731e6307 100644
--- a/docs-web/src/main/java/com/sismics/docs/rest/resource/TagResource.java
+++ b/docs-web/src/main/java/com/sismics/docs/rest/resource/TagResource.java
@@ -192,7 +192,7 @@ public class TagResource extends BaseResource {
                 throw new ClientException("ParentNotFound", MessageFormat.format("Parent not found: {0}", parentId));
             }
         }
-        
+
         // Create the tag
         TagDao tagDao = new TagDao();
         Tag tag = new Tag();
@@ -239,6 +239,7 @@ public class TagResource extends BaseResource {
      * @apiError (client) ValidationError Validation error
      * @apiError (client) SpacesNotAllowed Spaces are not allowed in tag name
      * @apiError (client) ParentNotFound Parent not found
+     * @apiError (client) CircularReference Circular reference in parent tag
      * @apiError (client) NotFound Tag not found
      * @apiPermission user
      * @apiVersion 1.5.0
@@ -275,16 +276,25 @@ public class TagResource extends BaseResource {
         }
         
         // Check the parent
+        TagDao tagDao = new TagDao();
         if (StringUtils.isEmpty(parentId)) {
             parentId = null;
         } else {
             if (!aclDao.checkPermission(parentId, PermType.READ, getTargetIdList(null))) {
                 throw new ClientException("ParentNotFound", MessageFormat.format("Parent not found: {0}", parentId));
             }
+
+            String parentTagId = parentId;
+            do {
+                Tag parentTag = tagDao.getById(parentTagId);
+                parentTagId = parentTag.getParentId();
+                if (parentTag.getId().equals(id)) {
+                    throw new ClientException("CircularReference", "Circular reference in parent tag");
+                }
+            } while (parentTagId != null);
         }
-        
+
         // Update the tag
-        TagDao tagDao = new TagDao();
         Tag tag = tagDao.getById(id);
         if (!StringUtils.isEmpty(name)) {
             tag.setName(name);
diff --git a/docs-web/src/main/webapp/src/app/docs/controller/tag/TagEdit.js b/docs-web/src/main/webapp/src/app/docs/controller/tag/TagEdit.js
index 1df1c2d2..35f2ded4 100644
--- a/docs-web/src/main/webapp/src/app/docs/controller/tag/TagEdit.js
+++ b/docs-web/src/main/webapp/src/app/docs/controller/tag/TagEdit.js
@@ -21,7 +21,15 @@ angular.module('docs').controller('TagEdit', function($scope, $stateParams, Rest
    */
   $scope.edit = function() {
     // Update the server
-    Restangular.one('tag', $scope.tag.id).post('', $scope.tag);
+    Restangular.one('tag', $scope.tag.id).post('', $scope.tag).then(function () {
+    }, function (e) {
+      if (e.data.type === 'CircularReference') {
+        var title = $translate.instant('tag.edit.circular_reference_title');
+        var msg = $translate.instant('tag.edit.circular_reference_message');
+        var btns = [{result: 'ok', label: $translate.instant('ok'), cssClass: 'btn-primary'}];
+        $dialog.messageBox(title, msg, btns);
+      }
+    });
   };
 
   /**
diff --git a/docs-web/src/main/webapp/src/locale/en.json b/docs-web/src/main/webapp/src/locale/en.json
index 7d83ef1d..e20d7514 100644
--- a/docs-web/src/main/webapp/src/locale/en.json
+++ b/docs-web/src/main/webapp/src/locale/en.json
@@ -219,7 +219,9 @@
       "name": "Name",
       "color": "Color",
       "parent": "Parent",
-      "info": "Permissions on this tag will also be applied to documents tagged <span class=\"label label-info\" ng-style=\"{ 'background': color }\">{{ name }}</span>"
+      "info": "Permissions on this tag will also be applied to documents tagged <span class=\"label label-info\" ng-style=\"{ 'background': color }\">{{ name }}</span>",
+      "circular_reference_title": "Circular reference",
+      "circular_reference_message": "The hierarchy of parent tags makes a loop, please choose another parent."
     }
   },
   "group": {
diff --git a/docs-web/src/test/java/com/sismics/docs/rest/TestTagResource.java b/docs-web/src/test/java/com/sismics/docs/rest/TestTagResource.java
index a8f8fee1..b8f4b5fa 100644
--- a/docs-web/src/test/java/com/sismics/docs/rest/TestTagResource.java
+++ b/docs-web/src/test/java/com/sismics/docs/rest/TestTagResource.java
@@ -45,6 +45,15 @@ public class TestTagResource extends BaseJerseyTest {
         String tag4Id = json.getString("id");
         Assert.assertNotNull(tag4Id);
 
+        // Create a circular reference
+        Response response = target().path("/tag/" + tag3Id).request()
+                .cookie(TokenBasedSecurityFilter.COOKIE_NAME, tag1Token)
+                .post(Entity.form(new Form()
+                        .param("name", "Tag3")
+                        .param("color", "#0000ff")
+                        .param("parent", tag4Id)));
+        Assert.assertEquals(Status.BAD_REQUEST, Status.fromStatusCode(response.getStatus()));
+
         // Get the tag
         json = target().path("/tag/" + tag4Id).request()
                 .cookie(TokenBasedSecurityFilter.COOKIE_NAME, tag1Token)
@@ -58,7 +67,7 @@ public class TestTagResource extends BaseJerseyTest {
         Assert.assertEquals(2, acls.size());
         
         // Create a tag with space (not allowed)
-        Response response = target().path("/tag").request()
+        response = target().path("/tag").request()
                 .cookie(TokenBasedSecurityFilter.COOKIE_NAME, tag1Token)
                 .put(Entity.form(new Form()
                         .param("name", "Tag 4")));
@@ -152,7 +161,7 @@ public class TestTagResource extends BaseJerseyTest {
                 .cookie(TokenBasedSecurityFilter.COOKIE_NAME, tag1Token)
                 .get(JsonObject.class);
         tags = json.getJsonArray("tags");
-        Assert.assertTrue(tags.size() == 2);
+        Assert.assertEquals(2, tags.size());
         Assert.assertEquals("Tag4", tags.getJsonObject(1).getString("name"));
         Assert.assertEquals("#00ff00", tags.getJsonObject(1).getString("color"));
         Assert.assertEquals(tag3Id, tags.getJsonObject(1).getString("parent"));
@@ -170,7 +179,7 @@ public class TestTagResource extends BaseJerseyTest {
                 .cookie(TokenBasedSecurityFilter.COOKIE_NAME, tag1Token)
                 .get(JsonObject.class);
         tags = json.getJsonArray("tags");
-        Assert.assertTrue(tags.size() == 2);
+        Assert.assertEquals(2, tags.size());
         Assert.assertEquals("UpdatedName", tags.getJsonObject(1).getString("name"));
         Assert.assertEquals("#0000ff", tags.getJsonObject(1).getString("color"));
         Assert.assertNull(tags.getJsonObject(1).get("parent"));
@@ -189,7 +198,7 @@ public class TestTagResource extends BaseJerseyTest {
                 .cookie(TokenBasedSecurityFilter.COOKIE_NAME, tag1Token)
                 .get(JsonObject.class);
         tags = json.getJsonArray("tags");
-        Assert.assertTrue(tags.size() == 2);
+        Assert.assertEquals(2, tags.size());
         Assert.assertEquals(tag3Id, tags.getJsonObject(1).getString("parent"));
 
         // Deletes a tag
@@ -202,7 +211,7 @@ public class TestTagResource extends BaseJerseyTest {
                 .cookie(TokenBasedSecurityFilter.COOKIE_NAME, tag1Token)
                 .get(JsonObject.class);
         tags = json.getJsonArray("tags");
-        Assert.assertTrue(tags.size() == 1);
+        Assert.assertEquals(1, tags.size());
         Assert.assertEquals("UpdatedName", tags.getJsonObject(0).getString("name"));
         Assert.assertNull(tags.getJsonObject(0).get("parent"));
     }