diff --git a/lib/dbh/dbh.class.php b/lib/dbh/dbh.class.php
index 3ffc1d5622..a8525764b0 100644
--- a/lib/dbh/dbh.class.php
+++ b/lib/dbh/dbh.class.php
@@ -383,8 +383,8 @@ class dbh
             case 'dm':
                 /* DATE convert to TO_CHAR. */
                 $sql = preg_replace("/\bDATE\(([^)]*)\)/",  "TO_CHAR($1, 'yyyy-mm-dd')", $sql, -1);
-                /* DATE_FORMAT convert to TO_CHAR. */
-                $sql = preg_replace("/\bDATE_FORMAT\(([^)]*)\)/",  "TO_CHAR($1, 'yyyy-mm-dd')", $sql, -1);
+                /* DATE_FORMAT(openedDate, '%Y-%m-%d') convert to TO_CHAR(openedDate, 'yyyy-mm-dd'). */
+                $sql = preg_replace('/DATE_FORMAT\((\w+),\s*'%Y-%m-%d'\)/',  "TO_CHAR($1, \'yyyy-mm-dd\')", $sql, -1);
 
                 return $sql;
 
diff --git a/module/bug/model.php b/module/bug/model.php
index 551a4f943b..48cfd52023 100644
--- a/module/bug/model.php
+++ b/module/bug/model.php
@@ -2409,7 +2409,7 @@ class bugModel extends model
      */
     public function getDataOfOpenedBugsPerDay()
     {
-        return $this->dao->select('DATE_FORMAT(openedDate, "%Y-%m-%d") AS name, COUNT(*) AS value')->from(TABLE_BUG)->where($this->reportCondition())->groupBy('name')->orderBy('openedDate')->fetchAll();
+        return $this->dao->select("DATE_FORMAT(openedDate, '%Y-%m-%d') AS name, COUNT(*) AS value")->from(TABLE_BUG)->where($this->reportCondition())->groupBy('name')->orderBy('openedDate')->fetchAll();
     }
 
     /**
@@ -2420,7 +2420,7 @@ class bugModel extends model
      */
     public function getDataOfResolvedBugsPerDay()
     {
-        return $this->dao->select('DATE_FORMAT(resolvedDate, "%Y-%m-%d") AS name, COUNT(*) AS value')->from(TABLE_BUG)
+        return $this->dao->select("DATE_FORMAT(resolvedDate, '%Y-%m-%d') AS name, COUNT(*) AS value")->from(TABLE_BUG)
             ->where($this->reportCondition())->groupBy('name')
             ->having('name != 0000-00-00')
             ->orderBy('resolvedDate')
@@ -2435,7 +2435,7 @@ class bugModel extends model
      */
     public function getDataOfClosedBugsPerDay()
     {
-        return $this->dao->select('DATE_FORMAT(closedDate, "%Y-%m-%d") AS name, COUNT(*) AS value')->from(TABLE_BUG)
+        return $this->dao->select("DATE_FORMAT(closedDate, '%Y-%m-%d') AS name, COUNT(*) AS value")->from(TABLE_BUG)
             ->where($this->reportCondition())->groupBy('name')
             ->having('name != 0000-00-00')
             ->orderBy('closedDate')->fetchAll();