diff --git a/Shape_detection/include/CGAL/Shape_detection/Efficient_RANSAC/Shape_base.h b/Shape_detection/include/CGAL/Shape_detection/Efficient_RANSAC/Shape_base.h
index 6afb0949552..21d21d13dab 100644
--- a/Shape_detection/include/CGAL/Shape_detection/Efficient_RANSAC/Shape_base.h
+++ b/Shape_detection/include/CGAL/Shape_detection/Efficient_RANSAC/Shape_base.h
@@ -623,7 +623,7 @@ namespace CGAL {
                                const std::ptrdiff_t n,
                                FT &low,
                                FT &high) {
-      const FT xn = double(x) * double(n);
+      const FT xn = FT(double(x) * double(n));
       const FT q = FT(xn * double(UN - x) * (UN - n) / (UN - 1));
       const FT sq = CGAL::sqrt(q);
       low  = (xn - sq) / UN;