diff --git a/plugins/constants.h b/plugins/constants.h
index 9edbe69..a9428d0 100644
--- a/plugins/constants.h
+++ b/plugins/constants.h
@@ -6,11 +6,15 @@
 #ifndef MK_CONSTANTS
 #define MK_CONSTANTS
 
-// This is necessary to get M_PI to work on windows
+// This is necessary to get M_PI and M_E to work on windows
 #ifndef M_PI
 #define M_PI 3.14159265358979323846
 #endif
 
+#ifndef M_E
+#define M_E 2.7182818284590452354
+#endif
+
 #ifndef M_SQRT2
 #define M_SQRT2 1.41421356237309504880
 #endif