diff --git a/vector.hpp b/vector.hpp
index f273e1e7..ed732543 100644
--- a/vector.hpp
+++ b/vector.hpp
@@ -80,7 +80,7 @@ namespace util {
         return {
             r,
             std::acos (c.z / r),
-            std::atan (c.y / c.z)
+            std::atan2 (c.y, c.x)
         };
     }