diff --git a/ncrypt/crypt_gpgme.c b/ncrypt/crypt_gpgme.c
index 8cd70fd6268..50c588a2755 100644
--- a/ncrypt/crypt_gpgme.c
+++ b/ncrypt/crypt_gpgme.c
@@ -3581,7 +3581,7 @@ static struct CryptKeyInfo *crypt_getkeybyaddr(struct Address *a,
   *forced_valid = 0;
 
   if (a && a->mailbox)
-    mutt_list_insert_tail(&hints, a->mailbox);
+    mutt_list_insert_tail(&hints, mutt_str_dup(a->mailbox));
   if (a && a->personal)
     crypt_add_string_to_hints(a->personal, &hints);
 
diff --git a/ncrypt/pgpkey.c b/ncrypt/pgpkey.c
index 665f9afe416..45ceb8b8ad4 100644
--- a/ncrypt/pgpkey.c
+++ b/ncrypt/pgpkey.c
@@ -369,7 +369,7 @@ struct PgpKeyInfo *pgp_getkeybyaddr(struct Address *a, KeyFlags abilities,
   struct PgpUid *q = NULL;
 
   if (a->mailbox)
-    mutt_list_insert_tail(&hints, a->mailbox);
+    mutt_list_insert_tail(&hints, mutt_str_dup(a->mailbox));
   if (a->personal)
     pgp_add_string_to_hints(a->personal, &hints);