diff --git a/defines.h b/defines.h
index 089e294..5385c92 100644
--- a/defines.h
+++ b/defines.h
@@ -23,7 +23,7 @@
 #define SSOCR2_DEFINES_H
 
 /* version number */
-#define VERSION "2.24.1"
+#define VERSION "2.24.1+"
 
 /* states */
 #define FIND_DARK 0
diff --git a/imgproc.c b/imgproc.c
index 2a9ec70..5357ce7 100644
--- a/imgproc.c
+++ b/imgproc.c
@@ -27,8 +27,11 @@
 /* string manipulation */
 #include <string.h>         /* strcasecmp, strcmp, strrchr */
 
-/* sin, cos */
-#include <math.h>
+/* trigonometry */
+#include <math.h>           /* sin, cos, M_PI */
+#ifndef M_PI                /* sometimes, M_PI is not defined */
+#define M_PI 3.14159265358979323846
+#endif
 
 /* my headers */
 #include "defines.h"        /* defines */