diff --git a/isso/db/__init__.py b/isso/db/__init__.py
index 7a10a74..cac31ee 100644
--- a/isso/db/__init__.py
+++ b/isso/db/__init__.py
@@ -2,8 +2,11 @@
 
 import sqlite3
 import logging
+import operator
 import os.path
 
+from collections import defaultdict
+
 logger = logging.getLogger("isso")
 
 from isso.db.comments import Comments
@@ -19,7 +22,7 @@ class SQLite3:
     a trigger for automated orphan removal.
     """
 
-    MAX_VERSION = 2
+    MAX_VERSION = 3
 
     def __init__(self, path, conf):
 
@@ -89,3 +92,25 @@ class SQLite3:
 
                 con.execute('PRAGMA user_version = 2')
                 logger.info("%i rows changed", con.total_changes)
+
+        # limit max. nesting level to 1
+        if self.version == 2:
+
+            first = lambda rv: list(map(operator.itemgetter(0), rv))
+
+            with sqlite3.connect(self.path) as con:
+                top = first(con.execute("SELECT id FROM comments WHERE parent IS NULL").fetchall())
+                flattened = defaultdict(set)
+
+                for id in top:
+
+                    ids = [id, ]
+
+                    while ids:
+                        rv = first(con.execute("SELECT id FROM comments WHERE parent=?", (ids.pop(), )))
+                        ids.extend(rv)
+                        flattened[id].update(set(rv))
+
+                for id in flattened.keys():
+                    for n in flattened[id]:
+                        con.execute("UPDATE comments SET parent=? WHERE id=?", (id, n))
diff --git a/isso/tests/test_db.py b/isso/tests/test_db.py
index be354e4..0b5db33 100644
--- a/isso/tests/test_db.py
+++ b/isso/tests/test_db.py
@@ -9,8 +9,11 @@ import sqlite3
 import tempfile
 
 from isso.db import SQLite3
+from isso.db.comments import Comments
 from isso.core import Config
 
+from isso.compat import iteritems
+
 
 class TestDBMigration(unittest.TestCase):
 
@@ -49,3 +52,56 @@ class TestDBMigration(unittest.TestCase):
         self.assertEqual(db.version, SQLite3.MAX_VERSION)
         self.assertEqual(db.preferences.get("session-key"),
                          "supersecretkey")
+
+    def test_limit_nested_comments(self):
+
+        tree = {
+            1: None,
+            2: None,
+               3: 2,
+                  4: 3,
+                  7: 3,
+               5: 2,
+            6: None
+        }
+
+        with sqlite3.connect(self.path) as con:
+            con.execute("PRAGMA user_version = 2")
+            con.execute("CREATE TABLE threads ("
+                        "    id INTEGER PRIMARY KEY,"
+                        "    uri VARCHAR UNIQUE,"
+                        "    title VARCHAR)")
+            con.execute("CREATE TABLE comments ("
+                        "    tid REFERENCES threads(id),"
+                        "    id INTEGER PRIMARY KEY,"
+                        "    parent INTEGER,"
+                        "    created FLOAT NOT NULL, modified FLOAT,"
+                        "    text VARCHAR, email VARCHAR, website VARCHAR,"
+                        "    mode INTEGER,"
+                        "    remote_addr VARCHAR,"
+                        "    likes INTEGER DEFAULT 0,"
+                        "    dislikes INTEGER DEFAULT 0,"
+                        "    voters BLOB)")
+
+            con.execute("INSERT INTO threads (uri, title) VALUES (?, ?)", ("/", "Test"))
+            for (id, parent) in iteritems(tree):
+                con.execute("INSERT INTO comments ("
+                            "   tid, parent, created)"
+                            "VALUEs (?, ?, ?)", (id, parent, id))
+
+        conf = Config.load(None)
+        db = SQLite3(self.path, conf)
+
+        flattened = [
+            (1, None),
+            (2, None),
+            (3, 2),
+            (4, 2),
+            (5, 2),
+            (6, None),
+            (7, 2)
+        ]
+
+        with sqlite3.connect(self.path) as con:
+            rv = con.execute("SELECT id, parent FROM comments ORDER BY created").fetchall()
+            self.assertEqual(flattened, rv)