diff --git a/lib/cartodb/utils/query-utils.js b/lib/cartodb/utils/query-utils.js
index ae1a2e2d..867db0cd 100644
--- a/lib/cartodb/utils/query-utils.js
+++ b/lib/cartodb/utils/query-utils.js
@@ -92,10 +92,13 @@ function columnSelector(columns) {
     if (!columns) {
         return '*';
     }
-    if (typeof(columns) === 'string') {
+    if (typeof columns === 'string') {
         return columns;
     }
-    return columns.map(name => `"${name}"`).join(', ');
+    if (Array.isArray(columns)) {
+        return columns.map(name => `"${name}"`).join(', ');
+    }
+    throw new TypeError(`Bad argument type for columns: ${typeof columns}`);
 }
 
 module.exports.getQuerySample = function(query, sampleProb, limit = null, randomSeed = 0.5, columns = null) {