diff --git a/plugins/views_plugin_query_default.inc b/plugins/views_plugin_query_default.inc
index 23f0eb1..886f5fe 100644
--- a/plugins/views_plugin_query_default.inc
+++ b/plugins/views_plugin_query_default.inc
@@ -1208,7 +1208,25 @@ class views_plugin_query_default extends views_plugin_query {
     $this->has_aggregate = FALSE;
     $non_aggregates = array();
 
-    list($non_aggregates) = $this->compile_fields($fields_array, $query);
+    $this->compile_fields($fields_array, $query);
+
+    foreach ($fields_array as $field){
+      if (!empty($field['table'])){
+        $name = $field['table'] . '.' . $field['field'];
+      }
+      else {
+        // Ignore SELECT variables, they cannot be used inside of GROUP BY statements as they are not part of any column.
+        if (preg_match("/^'.*'$/i", $field['field']) > 0){
+          continue;
+        }
+
+        $name = $field['field'];
+      }
+
+      if (!in_array($name, $non_aggregates)){
+        $non_aggregates[] = $name;
+      }
+    }
 
     if (count($this->having)) {
       $this->has_aggregate = TRUE;