diff --git a/lib/Git/IssueManager/Issue.pm b/lib/Git/IssueManager/Issue.pm
index 9cd0430..b246dd9 100644
--- a/lib/Git/IssueManager/Issue.pm
+++ b/lib/Git/IssueManager/Issue.pm
@@ -270,7 +270,7 @@ Default value is B<0>, meaning no estimate set.
 has 'estimated_time' => (is => 'rw', isa => 'Num', default => 0, trigger => sub {
             my ($self, $new, $old) = @_;
 
-            die("unknown value (" . $new . ")") unless $new > 0;
+            die("unknown value (" . $new . ")") unless $new >=0 ;
 });
 
 =attr working_time
@@ -283,7 +283,7 @@ The default value is B<0>.
 has 'working_time' => (is => 'rw', isa=>'Num', default => 0, trigger => sub {
             my ($self, $new, $old) = @_;
 
-            die("unknown value (" . $new . ")") unless $new > 0;
+            die("unknown value (" . $new . ")") unless $new >= 0;
 });