diff --git a/CMakeLists.txt b/CMakeLists.txt
index 43630f7e2..7294a1de7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -393,6 +393,9 @@ if (UNIX)
 		list(APPEND HDR_PRIVATE lib/getifaddrs.h)
 		list(APPEND SOURCES lib/getifaddrs.c)
 	endif()
+	if (NOT APPLE)
+		add_definitions(-D_POSIX_SOURCE=1)
+	endif()
 endif()
 
 if (CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX)
diff --git a/lib/lws-plat-unix.c b/lib/lws-plat-unix.c
index a7f96a36e..5283c077e 100644
--- a/lib/lws-plat-unix.c
+++ b/lib/lws-plat-unix.c
@@ -235,7 +235,7 @@ lws_plat_set_socket_options(struct libwebsocket_context *context, int fd)
 	optval = 1;
 #if !defined(__APPLE__) && !defined(__FreeBSD__) && !defined(__NetBSD__) && \
     !defined(__OpenBSD__)
-	if (setsockopt(fd, SOL_TCP, TCP_NODELAY, (const void *)&optval, optlen) < 0)
+	if (setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, (const void *)&optval, optlen) < 0)
 		return 1;
 #else
 	tcp_proto = getprotobyname("TCP");