diff --git a/lib/cartodb/models/aggregation/time-dimension.js b/lib/cartodb/models/aggregation/time-dimension.js
index 6fb09771..1a1909ed 100644
--- a/lib/cartodb/models/aggregation/time-dimension.js
+++ b/lib/cartodb/models/aggregation/time-dimension.js
@@ -32,7 +32,7 @@ function timeExpression(t, tz) {
 function epochExpression(epoch) {
     /* jshint maxcomplexity:8 */ // goddammit linter, I like this as is!!
     const format = /^(\d\d\d\d)(?:\-?(\d\d)(?:\-?(\d\d)(?:[T\s]?(\d\d)(?:(\d\d)(?:\:(\d\d))?)?)?)?)?$/;
-    const match  = epoch.match(format) || [];
+    const match  = (epoch || '').match(format) || [];
     const year   = match[1] || '0001';
     const month  = match[2] || '01';
     const day    = match[3] || '01';
@@ -165,7 +165,7 @@ const cyclicParts = {
 
 function cyclicSqlExpr(params) {
     const column = timeExpression(params.time, params.timezone);
-    return isoParts[params.grouping].replace(/\$t/g, column);
+    return cyclicParts[params.grouping].replace(/\$t/g, column);
 }
 
 const ACCEPTED_PARAMETERS = ['time', 'grouping', 'timezone', 'count', 'starting', 'format'];
@@ -256,7 +256,7 @@ const CLASSIFIERS = {
 };
 
 function isCyclic(groupBy) {
-    return groupBy.match(/.+By.+/);
+    return VALID_CYCLIC_GROUPINGS.includes(groupBy);
 }
 
 function classifierFor(params) {