diff --git a/pdf2book.py b/pdf2book.py
index d21ade8..57595b8 100755
--- a/pdf2book.py
+++ b/pdf2book.py
@@ -202,6 +202,9 @@ def make_zine(reader, lst):
     
 lst=get_reorder(number_of_pages, signature_size)
 if args.zine :
+    if number_of_pages != 16:
+        print("Error... when using '--zine' the input pdf must have 16 pages!")
+        exit(1)
     writer=make_zine(reader, lst)
 #    signature_size=zine
     outfile=args.pdf_file.split(".pdf")[0]+"_zine.pdf"