diff --git a/Geometrie.h b/Geometrie.h
index d13fa64..9b529dc 100644
--- a/Geometrie.h
+++ b/Geometrie.h
@@ -1,6 +1,11 @@
 #ifndef GEOMETRIE_H
 #define GEOMETRIE_H
 
+#ifndef M_PI
+#define M_PI (3.14159265358979323846)
+#endif
+
+
 struct position_t{
     double x_mm, y_mm;
     double angle_radian;