diff --git a/scripts/Modules/Util.pm b/scripts/Modules/Util.pm
index 712bf1a..1a09e92 100644
--- a/scripts/Modules/Util.pm
+++ b/scripts/Modules/Util.pm
@@ -365,7 +365,8 @@ sub pick_data_file {
     # \Q...\E treats ... as literal string
     my @files = sort grep { /^\Q$prefix\E.*\.csv$/ } find_files($dir);
 
-    return "$prefix.csv" unless @files > 1;
+    die "No $prefix CSV files found in $dir\n" unless @files;
+    return $files[0] if @files == 1;
 
     # Make sure the unfiltered file is at the top
     my @sorted = sort {