diff --git a/index.js b/index.js
index 68ec376..475f3b6 100644
--- a/index.js
+++ b/index.js
@@ -324,7 +324,7 @@ async function getArticleCounts(db, year) {
       printf('%02d', month) AS m
     FROM article
     WHERE year = @year
-    GROUP BY year_month
+    GROUP BY year, month
     ORDER BY year_month
   `).all({ year })
   return counts.map((c) => {