diff --git a/plot/plotRutils.c b/plot/plotRutils.c
index 9e252b72..98cb4d0c 100644
--- a/plot/plotRutils.c
+++ b/plot/plotRutils.c
@@ -28,6 +28,7 @@ static char rcsid[] __attribute__ ((unused)) = "$Header: /usr/cvsroot/magic-8.0/
 #include <string.h>
 #include <errno.h>
 #include <unistd.h>
+#include <math.h>
 
 #include "utils/magic.h"
 #include "utils/geometry.h"
@@ -40,8 +41,6 @@ static char rcsid[] __attribute__ ((unused)) = "$Header: /usr/cvsroot/magic-8.0/
 #include "textio/textio.h"
 #include "utils/utils.h"
 
-extern double sqrt();
-
 int rasFileByteCount = 0;
 /* A solid black stipple: */