updated for version 7.2a
diff --git a/src/os_win32.h b/src/os_win32.h
index 15e6160..b57ee23 100644
--- a/src/os_win32.h
+++ b/src/os_win32.h
@@ -28,6 +28,9 @@
 #ifndef HAVE_STRING_H
 # define HAVE_STRING_H
 #endif
+#ifndef HAVE_MATH_H
+# define HAVE_MATH_H
+#endif
 #define HAVE_STRCSPN
 #ifndef __GNUC__
 #define HAVE_STRICMP