diff --git a/admin.php b/admin.php
index 790189b..ed0ca81 100644
--- a/admin.php
+++ b/admin.php
@@ -59,6 +59,8 @@ public function html()
 
         echo '</table>';
 
+        echo '<p>' . $this->getLang('overviewHistory') . '</p>';
+
     }
 }
 
diff --git a/db/latest.version b/db/latest.version
index d00491f..0cfbf08 100644
--- a/db/latest.version
+++ b/db/latest.version
@@ -1 +1 @@
-1
+2
diff --git a/db/update0002.sql b/db/update0002.sql
new file mode 100644
index 0000000..8748d0e
--- /dev/null
+++ b/db/update0002.sql
@@ -0,0 +1,27 @@
+PRAGMA foreign_keys=OFF;
+
+CREATE TEMPORARY TABLE acks_temp
+(
+    page TEXT NOT NULL REFERENCES pages (page) ON DELETE CASCADE,
+    user TEXT NOT NULL,
+    ack  INT  NOT NULL,
+    PRIMARY KEY (page, user)
+);
+
+INSERT INTO acks_temp (page,user,ack) SELECT page,user,ack FROM acks;
+
+DROP TABLE acks;
+
+CREATE TABLE acks
+(
+    page TEXT NOT NULL REFERENCES pages (page),
+    user TEXT NOT NULL,
+    ack  INT  NOT NULL,
+    PRIMARY KEY (page, user, ack)
+);
+
+INSERT INTO acks (page,user,ack) SELECT page,user,ack FROM acks_temp;
+
+DROP TABLE acks_temp;
+
+PRAGMA foreign_keys=ON;
diff --git a/helper.php b/helper.php
index 25e815d..04cea57 100644
--- a/helper.php
+++ b/helper.php
@@ -172,7 +172,7 @@ public function saveAcknowledgement($page, $user)
         $sqlite = $this->getDB();
         if (!$sqlite) return false;
 
-        $sql = "REPLACE INTO acks (page, user, ack) VALUES (?,?, strftime('%s','now'))";
+        $sql = "INSERT INTO acks (page, user, ack) VALUES (?,?, strftime('%s','now'))";
 
         $result = $sqlite->query($sql, $page, $user);
         $sqlite->res_close($result);
@@ -199,9 +199,9 @@ public function getUserAssignments($user)
                 JOIN pages B
                 ON A.page = B.page
                 LEFT JOIN acks C
-                ON A.page = C.page
+                ON A.page = C.page AND ( (C.user = ? AND C.ack > B.lastmod) OR (C.user IS NOT ?) )
                 WHERE AUTH_ISMEMBER(A.assignee, ? , ?)
-                AND ( (C.user = ? AND C.ack < B.lastmod) OR (C.user IS NOT ?) )";
+                AND ack IS NULL";
 
         $result = $sqlite->query($sql, $user, implode('///', $groups), $user, $user);
         $assignments = $sqlite->res2arr($result);
@@ -220,7 +220,7 @@ public function getAcknowledgements()
         $sqlite = $this->getDB();
         if (!$sqlite) return false;
 
-        $sql = 'SELECT * FROM acks ORDER BY ack DESC';
+        $sql = 'SELECT page, user, max(ack) AS ack FROM acks GROUP BY user,page ORDER BY ack DESC';
         $result = $sqlite->query($sql);
         $acknowledgements = $sqlite->res2arr($result);
         $sqlite->res_close($result);
diff --git a/lang/en/lang.php b/lang/en/lang.php
index cef2651..5fa5d2b 100644
--- a/lang/en/lang.php
+++ b/lang/en/lang.php
@@ -17,6 +17,7 @@
 $lang['overviewPage'] = 'Page';
 $lang['overviewUser'] = 'User';
 $lang['overviewTime'] = 'Latest acknowledgement';
+$lang['overviewHistory'] = 'You can access previous acknowledgments by querying the database directly. Ask your administrator for assistance.';
 
 
 $lang['error sqlite plugin missing'] = 'The sqlite plugin is missing';