diff -r 91d1fc2a3a14 -r 33b6843fdf8a src/main/java/de/uapcore/lightpit/modules/UsersModule.java
--- a/src/main/java/de/uapcore/lightpit/modules/UsersModule.java	Fri May 22 17:26:27 2020 +0200
+++ b/src/main/java/de/uapcore/lightpit/modules/UsersModule.java	Fri May 22 21:23:57 2020 +0200
@@ -91,7 +91,7 @@
             setContentPage(req, Constants.JSP_COMMIT_SUCCESSFUL);
 
             LOG.debug("Successfully updated user {}", user.getUsername());
-        } catch (NoSuchElementException | NumberFormatException | SQLException ex) {
+        } catch (NoSuchElementException | IllegalArgumentException | SQLException ex) {
             // TODO: set request attribute with error text
             req.setAttribute("user", user);
             setContentPage(req, "user-form");