diff --git a/lib/models/SeminarCycleDate.php b/lib/models/SeminarCycleDate.php
index b8431a3fd41c5934f106265112ca6cb70d1e75d2..a63716e6d75fc5f1d80c16d0a41b97745956b648 100644
--- a/lib/models/SeminarCycleDate.php
+++ b/lib/models/SeminarCycleDate.php
@@ -174,7 +174,10 @@ class SeminarCycleDate extends SimpleORMap
      */
     protected function setSws($value)
     {
-        $this->content['sws'] = round(str_replace(',', '.', $value), 1);
+        if (is_string($value)) {
+            $value = (float) str_replace(',', '.', $value);
+        }
+        $this->content['sws'] = round($value, 1);
     }
 
     /**