diff --git a/libfprint/drivers/validity/validity_pack.h b/libfprint/drivers/validity/validity_pack.h
index a4856b84..19fc033b 100644
--- a/libfprint/drivers/validity/validity_pack.h
+++ b/libfprint/drivers/validity/validity_pack.h
@@ -63,6 +63,8 @@ validity_pack_one (FpiByteWriter *w,
       {
         const guint8 *d = va_arg (*ap, const guint8 *);
         gsize len = va_arg (*ap, gsize);
+        if (len == 0)
+          return TRUE;
         return fpi_byte_writer_put_data (w, d, len);
       }