diff --git a/CMakeLists.txt b/CMakeLists.txt
index 61a66b7c..07c0c800 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -102,7 +102,7 @@ elseif (APPLE)
 elseif (UNIX)
   set(HOSTOS "unix")
 
-  if (NOT ${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD")
+  if (NOT ${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD" AND NOT ${CMAKE_SYSTEM_NAME} STREQUAL "OpenBSD")
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -D_POSIX_C_SOURCE=200112L -D_XOPEN_SOURCE=600")
   endif ()
   if (${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
diff --git a/src/openssl/tls.c b/src/openssl/tls.c
index af1c3122..8730165a 100644
--- a/src/openssl/tls.c
+++ b/src/openssl/tls.c
@@ -48,19 +48,21 @@
 #include "context.h"
 #include "const-info.h"
 
-#ifdef USE_DANESSL
+#if defined(USE_DANESSL) || defined(LIBRESSL_VERSION_NUMBER)
 # include "ssl_dane/danessl.h"
 #endif
 
 #include "tls.h"
 
 /* Double check configure has worked as expected. */
+#ifndef LIBRESSL_VERSION_NUMBER
 #if defined(USE_DANESSL) && \
 	(defined(HAVE_SSL_DANE_ENABLE) || \
 	 defined(HAVE_OPENSSL_INIT_CRYPTO) || \
 	 defined(HAVE_SSL_CTX_DANE_ENABLE))
 #error Configure error USE_DANESSL defined with OpenSSL 1.1 functions!
 #endif
+#endif
 
 /* Cipher suites recommended in RFC7525. */
 static char const * const _getdns_tls_context_default_cipher_list =