diff --git a/sipa/blueprints/generic.py b/sipa/blueprints/generic.py
index 94843aed..79a495f8 100644
--- a/sipa/blueprints/generic.py
+++ b/sipa/blueprints/generic.py
@@ -152,7 +152,11 @@ def login():
             logger.info("Authentication failed: Wrong %s", cause, extra={
                 'tags': {'user': username, 'rate_critical': True}
             })
-            flash(gettext("Anmeldedaten fehlerhaft!"), "error")
+            if not username.islower():
+                flash(gettext("Anmeldedaten fehlerhaft oder Benutzername muss kleingeschrieben werden!"), "error")
+            else:
+                flash(gettext("Anmeldedaten fehlerhaft!"), "error")
+
         else:
             if isinstance(user, User):
                 login_user(user, remember=remember)
diff --git a/sipa/translations/de/LC_MESSAGES/messages.mo b/sipa/translations/de/LC_MESSAGES/messages.mo
index 6841f720..00a1beef 100644
Binary files a/sipa/translations/de/LC_MESSAGES/messages.mo and b/sipa/translations/de/LC_MESSAGES/messages.mo differ
diff --git a/sipa/translations/de/LC_MESSAGES/messages.po b/sipa/translations/de/LC_MESSAGES/messages.po
index 3017d39b..562aec5e 100644
--- a/sipa/translations/de/LC_MESSAGES/messages.po
+++ b/sipa/translations/de/LC_MESSAGES/messages.po
@@ -342,6 +342,9 @@ msgstr ""
 msgid "Anmeldedaten fehlerhaft!"
 msgstr ""
 
+msgid "Anmeldedaten fehlerhaft oder Benutzername muss kleingeschrieben werden!"
+msgstr ""
+
 msgid "Anmeldung erfolgreich!"
 msgstr ""
 
diff --git a/sipa/translations/en/LC_MESSAGES/messages.mo b/sipa/translations/en/LC_MESSAGES/messages.mo
index 8371bf4f..97eeace2 100644
Binary files a/sipa/translations/en/LC_MESSAGES/messages.mo and b/sipa/translations/en/LC_MESSAGES/messages.mo differ
diff --git a/sipa/translations/en/LC_MESSAGES/messages.po b/sipa/translations/en/LC_MESSAGES/messages.po
index 598a6329..243f7fd3 100644
--- a/sipa/translations/en/LC_MESSAGES/messages.po
+++ b/sipa/translations/en/LC_MESSAGES/messages.po
@@ -344,6 +344,9 @@ msgstr "Error during communication with the backend server ('%(name)s')"
 msgid "Anmeldedaten fehlerhaft!"
 msgstr "Authentication data incorrect!"
 
+msgid "Anmeldedaten fehlerhaft oder Benutzername muss kleingeschrieben werden!"
+msgstr "Authentication data incorrect or username has to be written in lowercase"
+
 msgid "Anmeldung erfolgreich!"
 msgstr "Authentication successful!"