diff --git a/etemplate/inc/class.so_sql.inc.php b/etemplate/inc/class.so_sql.inc.php
index e3a83ac757..2338c46e53 100644
--- a/etemplate/inc/class.so_sql.inc.php
+++ b/etemplate/inc/class.so_sql.inc.php
@@ -1156,6 +1156,8 @@ class so_sql
 				}
 				$alias = $col;
 				if (stripos($col, ' AS ')) list($col, $alias) = preg_split('/ +AS +/i', $col);
+				// do NOT group by constant expressions
+				if (preg_match('/^ *(-?[0-9]+|".*"|\'.*\'|NULL) *$/i', $col)) continue;
 				if (!in_array($col, $group_by_cols) && !in_array($alias, $group_by_cols))
 				{
 					$group_by_cols[] = $alias;
diff --git a/timesheet/inc/class.timesheet_bo.inc.php b/timesheet/inc/class.timesheet_bo.inc.php
index 10617c06c6..72b1d9bce8 100644
--- a/timesheet/inc/class.timesheet_bo.inc.php
+++ b/timesheet/inc/class.timesheet_bo.inc.php
@@ -559,9 +559,11 @@ class timesheet_bo extends so_sql_cf
 				$union_order[] = 'is_sum_'.$type;
 				$sum_extra_cols[$type]{0} = '1';
 				// the $type sum
-				parent::search($criteria,$sum_ts_id[$type].",'','','',MIN(ts_start),SUM(ts_duration) AS ts_duration,".
-					($this->quantity_sum ? "SUM(ts_quantity) AS ts_quantity" : '0').",0,NULL,0,0,0,0,0,SUM($total_sql) AS ts_total",
-					'GROUP BY '.$sum_sql[$type],$sum_extra_cols,$wildcard,$empty,$op,'UNION',$filter,$join,$need_full_no_count);
+				parent::search($criteria,array(
+					$sum_ts_id[$type],"''","''","''",'MIN(ts_start)','SUM(ts_duration) AS ts_duration',
+					($this->quantity_sum ? "SUM(ts_quantity) AS ts_quantity" : '0'),
+					'0','NULL','0','0','0','0','0',"SUM($total_sql) AS ts_total"
+				),'GROUP BY '.$sum_sql[$type],$sum_extra_cols,$wildcard,$empty,$op,'UNION',$filter,$join,$need_full_no_count);
 				$sum_extra_cols[$type]{0} = '0';
 			}
 			$union_order[] = 'ts_start '.$sort;