diff --git a/src/ChangeLog b/src/ChangeLog
index 4e378dc1852..5614b421a56 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,7 @@
 2000-09-25  Gerd Moellmann  <gerd@gnu.org>
 
+	* alloc.c (mark_image): Use GC_NILP instead of NILP.
+
 	* keyboard.c (show_help_echo): Set help_echo_showing_p.
 	(read_char): If help-echo is showing, preserve the echo area
 	when redisplaying.
diff --git a/src/alloc.c b/src/alloc.c
index 75466a787c7..5f08cd07d81 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -3769,7 +3769,7 @@ mark_image (img)
 {
   mark_object (&img->spec);
   
-  if (!NILP (img->data.lisp_val))
+  if (!GC_NILP (img->data.lisp_val))
     mark_object (&img->data.lisp_val);
 }