Don't confuse the Sun.
diff --git a/src/cmd/astro/astro.h b/src/cmd/astro/astro.h
index 3ac8c45..1c74a16 100644
--- a/src/cmd/astro/astro.h
+++ b/src/cmd/astro/astro.h
@@ -200,6 +200,7 @@
 extern	double	solstice(int);
 extern	void	star(void);
 extern	void	stars(void);
+#undef sun
 #define sun astrosun	/* not the machine! */
 extern	void	sun(void);
 extern	double	sunel(double);