diff --git a/bibcop.pl b/bibcop.pl
index 8879435..bd60811 100755
--- a/bibcop.pl
+++ b/bibcop.pl
@@ -428,7 +428,7 @@ sub check_month {
   my (%entry) = @_;
   if (exists $entry{'month'}) {
     my $month = $entry{'month'};
-    if (not $month =~ /^[1-9]|10|11|12$/) {
+    if (not $month =~ /^[1-9]|10|11|12|jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec$/) {
       return "The format of the 'month' is wrong"
     }
   }
diff --git a/perl-tests/checks.pl b/perl-tests/checks.pl
index 652dbb3..1e0cf83 100755
--- a/perl-tests/checks.pl
+++ b/perl-tests/checks.pl
@@ -115,6 +115,13 @@ package bibcop;
 check_passes($f, ('year' => '2022'));
 check_passes($f, ('year' => '1612'));
 
+$f = 'check_month';
+check_fails($f, ('month' => 'January'));
+check_fails($f, ('month' => '01'));
+check_passes($f, ('month' => 'jan'));
+check_passes($f, ('month' => '1'));
+check_passes($f, ('month' => '12'));
+
 $f = 'check_pages';
 check_fails($f, ('pages' => '1a'));
 check_fails($f, ('pages' => '40A'));