diff --git a/classes/timetable.php b/classes/timetable.php
index 5a225ca..d7a1792 100755
--- a/classes/timetable.php
+++ b/classes/timetable.php
@@ -126,7 +126,7 @@ class timetable {
 		$day = new \DateTime($this->monday->format('Y-m-d\TH:i:sP'));
 
 		for ($i=0; $i<$this->numdayweek; $i++) {
-			$sql = "date = '".$day->format('Ymd')."' AND ({$this->type}a LIKE '%{$this->name}%' OR {$this->type}b LIKE '%{$this->name}%')";
+			$sql = "date = '".$day->format('Ymd')."' AND ({$this->type}a RLIKE '(^|~){$this->name}($|~)' OR {$this->type}b RLIKE '(^|~){$this->name}($|~)')";
 			if ($result = $DB->get_records_select('timetable_substitution',$sql)) {
 				foreach ($result as $substitution) {
 					$this->data[$i+1][$substitution->period]['substitution'][] = $substitution;