diff --git a/UI/MailPartViewers/UIxMailPartEncryptedViewer.m b/UI/MailPartViewers/UIxMailPartEncryptedViewer.m
index f188f9ba6..d95feaced 100644
--- a/UI/MailPartViewers/UIxMailPartEncryptedViewer.m
+++ b/UI/MailPartViewers/UIxMailPartEncryptedViewer.m
@@ -104,6 +104,7 @@
   ERR_clear_error();
 
   msgBio = BIO_new_mem_buf ((void *) [signedData bytes], [signedData length]);
+  output = NULL;
 
   p7 = SMIME_read_PKCS7(msgBio, NULL);