diff --git a/src/per_corner_normals.cpp b/src/per_corner_normals.cpp
index 41fd34d..6e03142 100644
--- a/src/per_corner_normals.cpp
+++ b/src/per_corner_normals.cpp
@@ -15,7 +15,7 @@ void per_corner_normals(
 
   vertex_triangle_adjacency(F, static_cast<int>(V.rows()), VF);
 
-  double cos_threshold = std::cos(corner_threshold * M_PI / 180.0);
+  double cos_threshold = std::cos(corner_threshold * 3.14159265358979323846 / 180.0);
 
   /* Compute the area-weighted average of normals of faces with normals that deviate less than threshold. */
   for (int i = 0; i < F.rows(); i++) { /* For each face */