diff --git a/lib/isc/netmgr/tlsstream.c b/lib/isc/netmgr/tlsstream.c
index 169b391002..13789cd86a 100644
--- a/lib/isc/netmgr/tlsstream.c
+++ b/lib/isc/netmgr/tlsstream.c
@@ -496,6 +496,7 @@ tls_do_bio(isc_nmsocket_t *sock, isc_region_t *received_data,
 			}
 		}
 	}
+	errno = 0;
 	tls_status = SSL_get_error(sock->tlsstream.tls, rv);
 	saved_errno = errno;