diff --git a/dlib/image_transforms/spatial_filtering.h b/dlib/image_transforms/spatial_filtering.h
index b94bc0bd9..6a9aada1f 100644
--- a/dlib/image_transforms/spatial_filtering.h
+++ b/dlib/image_transforms/spatial_filtering.h
@@ -669,7 +669,7 @@ namespace dlib
 
         const rectangle area = get_rect(img);
 
-        // save width to avoid computing them over and over
+        // Save width to avoid computing it over and over.
         const long width = rect.width();