diff --git a/lib/cartodb/models/dataview/histogram.js b/lib/cartodb/models/dataview/histogram.js
index af18ea12..fdacbbe0 100644
--- a/lib/cartodb/models/dataview/histogram.js
+++ b/lib/cartodb/models/dataview/histogram.js
@@ -128,8 +128,8 @@ const nullsQueryTpl = ctx => `
     __cdb_nulls AS (
         SELECT
             count(*) AS __cdb_nulls_count
-        FROM (${it._query}) __cdb_histogram_nulls
-        WHERE ${it._column} IS NULL
+        FROM (${ctx._query}) __cdb_histogram_nulls
+        WHERE ${ctx._column} IS NULL
     )
 `;