diff --git a/tools/gif2tiff.c b/tools/gif2tiff.c
index 17f7a19..375b152 100644
--- a/tools/gif2tiff.c
+++ b/tools/gif2tiff.c
@@ -333,6 +333,10 @@ readraster(void)
     int status = 1;
 
     datasize = getc(infile);
+
+    if (datasize > 12)
+        return 0;
+
     clear = 1 << datasize;
     eoi = clear + 1;
     avail = clear + 2;