diff --git a/zurb_foundation.theme b/zurb_foundation.theme
index e9ed30e..28b451e 100644
--- a/zurb_foundation.theme
+++ b/zurb_foundation.theme
@@ -301,18 +301,18 @@ function zurb_foundation_preprocess_page(&$variables) {

   // Dynamic sidebars
   if (!empty($left) && !empty($right)) {
-    $variables['main_grid'] = 'large-6 large-push-3';
-    $variables['sidebar_first_grid'] = 'large-3 large-pull-6';
-    $variables['sidebar_sec_grid'] = 'large-3';
+    $variables['main_grid'] = 'medium-6 medium-push-3';
+    $variables['sidebar_first_grid'] = 'medium-3 medium-pull-6';
+    $variables['sidebar_sec_grid'] = 'medium-3';
   }
   elseif (empty($left) && !empty($right)) {
-    $variables['main_grid'] = 'large-9';
+    $variables['main_grid'] = 'medium-9';
     $variables['sidebar_first_grid'] = '';
-    $variables['sidebar_sec_grid'] = 'large-3';
+    $variables['sidebar_sec_grid'] = 'medium-3';
   }
   elseif (!empty($left) && empty($right)) {
-    $variables['main_grid'] = 'large-9 large-push-3';
-    $variables['sidebar_first_grid'] = 'large-3 large-pull-9';
+    $variables['main_grid'] = 'medium-9 medium-push-3';
+    $variables['sidebar_first_grid'] = 'medium-3 medium-pull-9';
     $variables['sidebar_sec_grid'] = '';
   }
   else {