diff --git a/lib/libstereo/src/costs/census.hpp b/lib/libstereo/src/costs/census.hpp
index 2690ddfa7ece87c50687905ba955cc08df30e709..cb577bfd7d7afcb42688d2d7749cf6f83a35b6e0 100644
--- a/lib/libstereo/src/costs/census.hpp
+++ b/lib/libstereo/src/costs/census.hpp
@@ -58,7 +58,7 @@ namespace impl {
 	 */
 	template<int SIZE>
 	struct NormalizedHammingCost : DSImplBase<float> {
-		static_assert(SIZE%64 == 0);
+		static_assert(SIZE%64 == 0, "size must be multiple of 64");
 
 		typedef float Type;