diff -Naur tk8.4.15.orig/generic/tkImgGIF.c tk8.4.15/generic/tkImgGIF.c
--- tk8.4.15.orig/generic/tkImgGIF.c	2006-03-27 21:13:56.000000000 +0900
+++ tk8.4.15/generic/tkImgGIF.c	2007-09-16 09:56:25.000000000 +0900
@@ -995,7 +995,7 @@
 	 */
 	if (interlace) {
 	    ypos += interlaceStep[pass];
-	    while (ypos >= height) {
+	    while (ypos >= rows) {
 		pass++;
 		if (pass > 3) {
 		    return TCL_OK;