diff --git a/classes/image_types_phosphor.bbclass b/classes/image_types_phosphor.bbclass
index 10388d2..39534db 100644
--- a/classes/image_types_phosphor.bbclass
+++ b/classes/image_types_phosphor.bbclass
@@ -324,7 +324,11 @@
 
     def _append_image(imgpath, start_kb, finish_kb):
         imgsize = os.path.getsize(imgpath)
-        if imgsize > (finish_kb - start_kb) * 1024:
+        maxsize = (finish_kb - start_kb) * 1024
+        bb.debug(1, 'Considering file size=' + str(imgsize) + ' name=' + imgpath)
+        bb.debug(1, 'Spanning start=' + str(start_kb) + 'K end=' + str(finish_kb) + 'K')
+        bb.debug(1, 'Compare needed=' + str(imgsize) + ' available=' + str(maxsize) + ' margin=' + str(maxsize - imgsize))
+        if imgsize > maxsize:
             bb.fatal("Image '%s' is too large!" % imgpath)
 
         subprocess.check_call(['dd', 'bs=1k', 'conv=notrunc',