diff --git a/ChangeLog b/ChangeLog
index 0dd07e8..c1b5fcc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2018-02-12  NIIBE Yutaka  <gniibe@fsij.org>
+
+	* src/openpgp-do.c (rw_kdf): Return 0 when NULL.
+
 2018-01-23  NIIBE Yutaka  <gniibe@fsij.org>
 
 	* VERSION: 1.2.8.
diff --git a/src/openpgp-do.c b/src/openpgp-do.c
index a9fb771..8fceb9d 100644
--- a/src/openpgp-do.c
+++ b/src/openpgp-do.c
@@ -860,7 +860,11 @@ rw_kdf (uint16_t tag, int with_tag, const uint8_t *data, int len, int is_write)
     }
   else
     {
-      copy_do_1 (tag, do_ptr[NR_DO_KDF], with_tag);
+      if (do_ptr[NR_DO_KDF])
+	copy_do_1 (tag, do_ptr[NR_DO_KDF], with_tag);
+      else
+	return 0;
+
       return 1;
     }
 }