diff --git a/doc/geos.sgml b/doc/geos.sgml
index 8e50a2605..cb849c389 100644
--- a/doc/geos.sgml
+++ b/doc/geos.sgml
@@ -48,7 +48,7 @@ changed between <tt/tgi_init/ and <tt/tgi_done/.
 It is safe to use these standard includes and their contents:
 <tt/assert.h, conio.h, dio.h, errno.h, em.h, geos.h, joystick.h, modload.h, mouse.h, stdlib.h, string.h, tgi.h, time.h/
 <p>
-For <tt/time.h/ functions <tt/systime()/ and <tt/clock()/ note that the resolution is one second.
+For <tt/time.h/ functions <tt/clock()/ and <tt/clock_gettime()/ note that the resolution is one second.
 <p>
 Functions from the headers above are either standard C library functions or cc65-specific, in
 either case they are not GEOS specific and so they are not described here.