--- tk8.5a6/generic/tkImgGIF.c~	2007-10-18 12:39:39.000000000 -0400
+++ tk8.5a6/generic/tkImgGIF.c	2007-10-18 12:39:39.000000000 -0400
@@ -1032,7 +1032,7 @@ ReadImage(
 
 	if (interlace) {
 	    ypos += interlaceStep[pass];
-	    while (ypos >= height) {
+	    while (ypos >= rows) {
 		pass++;
 		if (pass > 3) {
 		    return TCL_OK;