diff --git a/src/ifcgeom/mapping/IfcCurveSegment.cpp b/src/ifcgeom/mapping/IfcCurveSegment.cpp
index 9f15745352..e87c69d6bc 100644
--- a/src/ifcgeom/mapping/IfcCurveSegment.cpp
+++ b/src/ifcgeom/mapping/IfcCurveSegment.cpp
@@ -275,10 +275,10 @@ class cant_adjuster : public GEOMETRY_ADJUSTER {
        double cant = parent_curve_point.col(3)(1);
        auto tilt = -atan2(fabs(h), cant);
 
-       // Create a transformation matrix
+       // Create a transformation matrix for twist about the RefDirection (x-axis)
        Eigen::Matrix4d m = Eigen::Matrix4d::Identity();
-       m.col(2)(1) = cos(tilt);
-       m.col(2)(2) = sin(tilt);
+       m.col(2)(2) = cos(tilt);
+       m.col(2)(3) = sin(tilt);
 
        // apply cant tilt to the parent curve point
        Eigen::Matrix4d p = m * parent_curve_point;
diff --git a/src/ifcgeom/mapping/IfcFixedReferenceSweptAreaSolid.cpp b/src/ifcgeom/mapping/IfcFixedReferenceSweptAreaSolid.cpp
index 6f349d7675..49997f355f 100644
--- a/src/ifcgeom/mapping/IfcFixedReferenceSweptAreaSolid.cpp
+++ b/src/ifcgeom/mapping/IfcFixedReferenceSweptAreaSolid.cpp
@@ -71,6 +71,7 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcFixedReferenceSweptAreaSolid
 			ss << m4;
 			auto s = ss.str();
 			std::wcout << s.c_str() << std::endl;
+            std::wcout << "determinant: " << m4.determinant() << std::endl;
 
 			Eigen::Matrix4d m4b = Eigen::Matrix4d::Identity();
 			bool is_directrix_derived = false;