Index: src/tls/OFGnuTLSTLSStream.m
==================================================================
--- src/tls/OFGnuTLSTLSStream.m
+++ src/tls/OFGnuTLSTLSStream.m
@@ -127,15 +127,17 @@
 	[super dealloc];
 }
 
 - (void)close
 {
+	if (_session == NULL)
+		@throw [OFNotOpenException exceptionWithObject: self];
+
 	if (_handshakeDone)
 		gnutls_bye(_session, GNUTLS_SHUT_WR);
 
-	if (_session != NULL)
-		gnutls_deinit(_session);
+	gnutls_deinit(_session);
 
 	if (_credentials != NULL)
 		gnutls_certificate_free_credentials(_credentials);
 
 	_session = NULL;