diff --git a/dlib/image_keypoint/hog.h b/dlib/image_keypoint/hog.h
index ed484d56f..635d22321 100644
--- a/dlib/image_keypoint/hog.h
+++ b/dlib/image_keypoint/hog.h
@@ -145,18 +145,6 @@ namespace dlib
             long col
         ) const
         {
-            // make sure requires clause is not broken
-            DLIB_ASSERT( 0 <= row && row < nr() &&
-                         0 <= col && col < nc(),
-                "\t rectangle hog_image::get_block_rect()"
-                << "\n\t invalid row or col argument"
-                << "\n\t row:  " << row
-                << "\n\t col:  " << col 
-                << "\n\t nr(): " << nr() 
-                << "\n\t nc(): " << nc() 
-                << "\n\t this: " << this
-                );
-
             row *= cell_stride;
             col *= cell_stride;
 
diff --git a/dlib/image_keypoint/hog_abstract.h b/dlib/image_keypoint/hog_abstract.h
index 56786bfe7..9314f422b 100644
--- a/dlib/image_keypoint/hog_abstract.h
+++ b/dlib/image_keypoint/hog_abstract.h
@@ -219,12 +219,10 @@ namespace dlib
             long col
         ) const;
         /*!
-            requires
-                - 0 <= row < nr()
-                - 0 <= col < nc()
             ensures
                 - returns a rectangle that tells you what part of the original image is associated
-                  with a particular HOG block.
+                  with a particular HOG block.  That is, what part of the input image is associated
+                  with (*this)(row,col).
                 - The returned rectangle will be cell_size*block_size pixels wide and tall.
         !*/