--- tiff-4.0.6/tools/gif2tiff.c	2016-04-06 15:43:01.586048341 +0200
+++ tiff-4.0.6/tools/gif2tiff.c	2016-04-06 15:48:05.523207710 +0200
@@ -349,7 +349,7 @@
     int status = 1;
 
     (void) getc(infile);
-    while ((count = getc(infile)) && count <= 255)
+    while ((count = getc(infile)) && count >= 0 && count <= 255)
         if (fread(buf, 1, count, infile) != (size_t) count) {
             fprintf(stderr, "short read from file %s (%s)\n",
                     filename, strerror(errno));