diff --git a/inc/medleyfp.h b/inc/medleyfp.h
index 34f671f..5842ac6 100755
--- a/inc/medleyfp.h
+++ b/inc/medleyfp.h
@@ -105,6 +105,7 @@ volatile extern int  FP_error;
 #define FPTEST(result) ((!finite(result)) || isnan(result))
 
 #elif defined(MACOSX) || defined(FREEBSD)
+#include <math.h>
 #define FPCLEAR
 #define FPTEST(result) (!isfinite(result))