diff --git a/articles.bib b/articles.bib
index 849df8e..7558445 100644
--- a/articles.bib
+++ b/articles.bib
@@ -12259,7 +12259,7 @@ @Article{MarCavHer2023repr
   journal      = ec,
   year         = 2023,
   pages        = {1--35},
-  month        = 11,
+  month        = nov,
   issn         = {1063-6560},
   doi          = {10.1162/evco_a_00317},
   publisher    = {MIT Press},
diff --git a/test/fast_check.sh b/test/fast_check.sh
index 925a6c0..6c6a630 100755
--- a/test/fast_check.sh
+++ b/test/fast_check.sh
@@ -91,6 +91,7 @@ FILES=$@
 
 
 check_bad_thing "^\s*\(author\|editor\)\s\+=.*[[:space:]\"{][[:space:]]*[A-Z]\.\([A-Z]\.\)\+" "Author or editor initials must be separated by a space"
+check_bad_thing "^\s*month\s*=\s*[{\"]\?[0-9]" "Please do not use numbers for 'month', use jan, feb, mar, ..., nov, dec." "-e"
 check_bad_thing "^\s*\(biburl\|timestamp\|article-number\|copyright\)" "Please remove these fields" "--ignore-case -e"
 check_bad_thing "^\s*journaltitle" "'journaltitle' should be just 'journal'" "--ignore-case -e"
 check_bad_thing "doi[[:space:]]*=.\+http" "the doi field should not be an URL"