diff --git a/lib/models/SeminarCycleDate.class.php b/lib/models/SeminarCycleDate.class.php
index f384426895455a32e5b0fbb79972146592105304..2629525a9e5b4da7769b3a6fa9dfee9dbec15053 100644
--- a/lib/models/SeminarCycleDate.class.php
+++ b/lib/models/SeminarCycleDate.class.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);
     }
 
     /**