diff --git a/toolbox/test/channel_view.cpp b/toolbox/test/channel_view.cpp
index fe42b38a4..c41930435 100644
--- a/toolbox/test/channel_view.cpp
+++ b/toolbox/test/channel_view.cpp
@@ -34,10 +34,10 @@ BOOST_AUTO_TEST_CASE(channel_view_test)
         "");
 
     kth_channel_view_t const kth0 = bg::kth_channel_view<0>(bg::const_view(img));
-    BOOST_TEST(kth0.num_channels() == 1);
+    BOOST_TEST(kth0.num_channels() == 1u);
 
     channel_view_t const red = bg::channel_view<bg::red_t>(bg::const_view(img));
-    BOOST_TEST(red.num_channels() == 1);
+    BOOST_TEST(red.num_channels() == 1u);
 }
 
 BOOST_AUTO_TEST_SUITE_END()