diff --git a/modules/comment/comment.class.php b/modules/comment/comment.class.php
index c06bb0ee9..d7b4ffde9 100644
--- a/modules/comment/comment.class.php
+++ b/modules/comment/comment.class.php
@@ -105,6 +105,11 @@ class comment extends ModuleObject
 			return true;
 		}
 
+		if(!$oDB->isIndexExists("comments", "idx_parent_srl"))
+		{
+			return true;
+		}
+
 		return FALSE;
 	}
 
@@ -185,6 +190,11 @@ class comment extends ModuleObject
 			$oDB->addColumn('comment_declared_log',"declare_message","text");
 		}
 
+		if(!$oDB->isIndexExists("comments", "idx_parent_srl"))
+		{
+			$oDB->addIndex('comments', 'idx_parent_srl', array('parent_srl'));
+		}
+
 		return new Object(0, 'success_updated');
 	}
 
diff --git a/modules/comment/schemas/comments.xml b/modules/comment/schemas/comments.xml
index 7acecd447..cf9a31f02 100644
--- a/modules/comment/schemas/comments.xml
+++ b/modules/comment/schemas/comments.xml
@@ -2,7 +2,7 @@
     <column name="comment_srl" type="number" size="11" notnull="notnull" primary_key="primary_key" />
     <column name="module_srl" type="number" size="11" default="0" notnull="notnull" index="idx_module_srl" />
     <column name="document_srl" type="number" size="11" default="0" notnull="notnull" index="idx_document_srl" />
-    <column name="parent_srl" type="number" size="11" default="0" notnull="notnull" />
+    <column name="parent_srl" type="number" size="11" default="0" notnull="notnull" index="idx_parent_srl" />
     <column name="is_secret" type="char" size="1" default="N" notnull="notnull" />
     <column name="content" type="bigtext" notnull="notnull" />
     <column name="voted_count" type="number" size="11" default="0" notnull="notnull" index="idx_voted_count" />