diff --git a/libs/geom/include/psemek/geom/math.hpp b/libs/geom/include/psemek/geom/math.hpp
index 81586461..71b559b1 100644
--- a/libs/geom/include/psemek/geom/math.hpp
+++ b/libs/geom/include/psemek/geom/math.hpp
@@ -60,7 +60,7 @@ namespace psemek::geom
 	template <typename T>
 	T acos_over_sqrt_1_minus_x2(T const & x)
 	{
-		auto t = std::sqrt(T{1} - x * x);
+		auto t = std::sqrt(std::max(T{0}, T{1} - x * x));
 		if (t < std::numeric_limits<T>::epsilon())
 			return T{1};
 		return std::acos(x) / t;