diff --git a/libs/geom/include/psemek/geom/math.hpp b/libs/geom/include/psemek/geom/math.hpp
index 21066c2b..f3554977 100644
--- a/libs/geom/include/psemek/geom/math.hpp
+++ b/libs/geom/include/psemek/geom/math.hpp
@@ -45,7 +45,7 @@ namespace psemek::geom
 	}
 
 	template <typename X, typename T>
-	X lerp(X const & x0, X const & x1, T const & t)
+	auto lerp(X const & x0, X const & x1, T const & t) -> decltype(x0 * t)
 	{
 		return x0 * (T(1) - t) + x1 * t;
 	}