diff --git a/src/PVE/CalendarEvent.pm b/src/PVE/CalendarEvent.pm
index a053f38..b27e968 100644
--- a/src/PVE/CalendarEvent.pm
+++ b/src/PVE/CalendarEvent.pm
@@ -5,6 +5,7 @@ use warnings;
 use Data::Dumper;
 use Time::Local;
 use PVE::JSONSchema;
+use PVE::Tools qw(trim);
 
 # Note: This class implements a parser/utils for systemd like calender exents
 # Date specification is currently not implemented
@@ -36,6 +37,12 @@ sub pve_verify_calendar_event {
 sub parse_calendar_event {
     my ($event) = @_;
 
+    $event = trim($event);
+
+    if ($event eq '') {
+	die "unable to parse calendar event - event is empty\n";
+    }
+
     my $parse_single_timespec = sub {
 	my ($p, $max, $matchall_ref, $res_hash) = @_;
 
diff --git a/test/calendar_event_test.pl b/test/calendar_event_test.pl
index 9c2bf46..5416255 100755
--- a/test/calendar_event_test.pl
+++ b/test/calendar_event_test.pl
@@ -145,6 +145,18 @@ my $tests = [
      '0..80',
      { error => "range end '80' out of range" },
     ],
+    [
+     ' mon 0 0 0',
+     { error => "unable to parse calendar event - unused parts" },
+    ],
+    [
+     '',
+     { error => "unable to parse calendar event - event is empty" },
+    ],
+    [
+     ' mon 0 0',
+     { error => "unable to parse calendar event - unused parts" },
+    ],
 ];
 
 foreach my $test (@$tests) {