diff --git a/include/upm_math.h b/include/upm_math.h
index 451c05c7..de423ed1 100644
--- a/include/upm_math.h
+++ b/include/upm_math.h
@@ -32,6 +32,10 @@ extern "C" {
 #include <math.h>
 #endif
 
+#ifndef M_PI
+#define M_PI           (3.14159265358979323846)
+#endif
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/rotary/rotary_fti.c b/src/rotary/rotary_fti.c
index 33428727..2eedf724 100644
--- a/src/rotary/rotary_fti.c
+++ b/src/rotary/rotary_fti.c
@@ -26,6 +26,7 @@
 
 #include "rotary.h"
 #include "upm_fti.h"
+#include "upm_math.h"
 
 /** 
  * This file implements the Function Table Interface (FTI) for this sensor