diff --git a/brave/components/ntp_background_images/browser/view_counter_model.h b/brave/components/ntp_background_images/browser/view_counter_model.h
index 940d8c4e47..13c0b9561c 100644
--- a/brave/components/ntp_background_images/browser/view_counter_model.h
+++ b/brave/components/ntp_background_images/browser/view_counter_model.h
@@ -23,10 +23,10 @@ class ViewCounterModel {
 
   // Set each campaigns total image count.
   void SetCampaignsTotalBrandedImageCount(
-      const std::vector<size_t>& campaigns_total_image_count);
+      const std::vector<std::size_t>& campaigns_total_image_count);
 
   // Returns current campaign index and its bg index.
-  std::tuple<size_t, size_t> GetCurrentBrandedImageIndex() const;
+  std::tuple<std::size_t, std::size_t> GetCurrentBrandedImageIndex() const;
 
   int current_wallpaper_image_index() const {
     return current_wallpaper_image_index_;
@@ -68,10 +68,10 @@ class ViewCounterModel {
   int count_to_branded_wallpaper_ = 0;
   bool always_show_branded_wallpaper_ = false;
   bool show_branded_wallpaper_ = true;
-  size_t current_campaign_index_ = 0;
-  size_t total_campaign_count_ = 0;
-  std::vector<size_t> campaigns_total_branded_image_count_;
-  std::vector<size_t> campaigns_current_branded_image_index_;
+  std::size_t current_campaign_index_ = 0;
+  std::size_t total_campaign_count_ = 0;
+  std::vector<std::size_t> campaigns_total_branded_image_count_;
+  std::vector<std::size_t> campaigns_current_branded_image_index_;
 
   // For NTP BI.
   int current_wallpaper_image_index_ = 0;