diff -ur mutt-1.9.0.orig/init.h mutt-1.9.0/init.h
--- mutt-1.9.0.orig/init.h	2017-09-04 16:48:21.409528002 +0200
+++ mutt-1.9.0/init.h	2017-09-04 16:49:26.505093636 +0200
@@ -3510,7 +3510,7 @@
   */
 #  endif /* defined HAVE_SSL_PARTIAL_CHAIN */
 # endif /* defined USE_SSL_OPENSSL */
-  { "ssl_ciphers", DT_STR, R_NONE, UL &SslCiphers, UL 0 },
+  { "ssl_ciphers", DT_STR, R_NONE, UL &SslCiphers, UL "@SYSTEM" },
   /*
   ** .pp
   ** Contains a colon-seperated list of ciphers to use when using SSL.
diff -ur mutt-1.9.0.orig/mutt_ssl_gnutls.c mutt-1.9.0/mutt_ssl_gnutls.c
--- mutt-1.9.0.orig/mutt_ssl_gnutls.c	2017-09-04 16:48:21.403528134 +0200
+++ mutt-1.9.0/mutt_ssl_gnutls.c	2017-09-04 16:51:16.081679141 +0200
@@ -286,6 +286,8 @@
   else
     safe_strcat (priority, priority_size, "NORMAL");
 
+if (SslCiphers && strcmp(SslCiphers, "@SYSTEM"))
+{
   if (! option(OPTTLSV1_2))
   {
     nproto--;
@@ -313,6 +315,7 @@
     FREE (&priority);
     return -1;
   }
+}
 
   if ((err = gnutls_priority_set_direct (data->state, priority, NULL)) < 0)
   {
