diff --git a/dlib/image_transforms/spatial_filtering.h b/dlib/image_transforms/spatial_filtering.h
index 339c5fce5..03efe5b69 100644
--- a/dlib/image_transforms/spatial_filtering.h
+++ b/dlib/image_transforms/spatial_filtering.h
@@ -124,9 +124,7 @@ namespace dlib
         const in_image_type& in_img,
         out_image_type& out_img,
         const matrix_exp<EXP>& filter,
-        T scale,
-        bool use_abs = false,
-        bool add_to = false
+        T scale
     )
     {
         COMPILE_TIME_ASSERT( pixel_traits<typename in_image_type::type>::has_alpha == false );
diff --git a/dlib/image_transforms/spatial_filtering_abstract.h b/dlib/image_transforms/spatial_filtering_abstract.h
index 5ce3a8b4c..eeead68b6 100644
--- a/dlib/image_transforms/spatial_filtering_abstract.h
+++ b/dlib/image_transforms/spatial_filtering_abstract.h
@@ -36,6 +36,9 @@ namespace dlib
             - scale != 0
             - filter.nr() % 2 == 1  (i.e. must be odd)
             - filter.nc() % 2 == 1  (i.e. must be odd)
+            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
+                - use_abs == false && add_to == false
+                  (i.e. You can only use the use_abs and add_to options with grayscale images)
         ensures
             - Applies the given spatial filter to in_img and stores the result in out_img (i.e.
               cross-correlates in_img with filter).  Also divides each resulting pixel by scale.  
@@ -88,6 +91,9 @@ namespace dlib
             - is_vector(col_filter) == true
             - row_filter.size() % 2 == 1  (i.e. must be odd)
             - col_filter.size() % 2 == 1  (i.e. must be odd)
+            - if (pixel_traits<typename in_image_type::type>::grayscale == false) then
+                - use_abs == false && add_to == false
+                  (i.e. You can only use the use_abs and add_to options with grayscale images)
         ensures
             - Applies the given separable spatial filter to in_img and stores the result in out_img.  
               Also divides each resulting pixel by scale.  Calling this function has the same
diff --git a/dlib/test/queue.cpp b/dlib/test/queue.cpp
index c407fbb6a..efcdf6054 100644
--- a/dlib/test/queue.cpp
+++ b/dlib/test/queue.cpp
@@ -354,7 +354,7 @@ namespace
             for (int i = 0; i < 100; ++i)
             {
                 int a = 9;
-                go.remove_any(a);
+                q.remove_any(a);
                 DLIB_TEST(a == 3);
             }
             DLIB_TEST(go.size() == 0);
diff --git a/dlib/test/stack.cpp b/dlib/test/stack.cpp
index bc64aa2a4..0b92eaeb9 100644
--- a/dlib/test/stack.cpp
+++ b/dlib/test/stack.cpp
@@ -260,7 +260,7 @@ namespace
             for (int i = 0; i < 100; ++i)
             {
                 int a = 9;
-                go.remove_any(a);
+                a1.remove_any(a);
                 DLIB_TEST(a == 3);
             }
             DLIB_TEST(go.size() == 0);