diff --git a/CMakeLists.txt b/CMakeLists.txt
index 571c961d1..d50bf1235 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -238,6 +238,12 @@ if(ENABLE_LARGEFILE)
   add_definitions(-D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -D_LARGE_FILES)
 endif()
 
+# _XPG4_2 is needed for macros like CMSG_SPACE
+# __EXTENSIONS__ is needed for constants like NI_MAXHOST and for struct timeval
+if(CMAKE_HOST_SOLARIS)
+  add_definitions(-D_XPG4_2 -D__EXTENSIONS__)
+endif()
+
 # Check for libgcrypt
 pkg_check_modules(LIBGCRYPT REQUIRED libgcrypt)
 include_directories(${LIBGCRYPT_INCLUDE_DIRS})
diff --git a/src/core/core-network.c b/src/core/core-network.c
index 20dfb7faa..01e9a2792 100644
--- a/src/core/core-network.c
+++ b/src/core/core-network.c
@@ -28,13 +28,6 @@
 #include "config.h"
 #endif
 
-/* _XPG4_2 is needed on SunOS for macros like CMSG_SPACE */
-/* __EXTENSIONS__ is needed on SunOS for constants like NI_MAXHOST */
-#ifdef __sun
-#define _XPG4_2
-#define __EXTENSIONS__
-#endif
-
 #include <unistd.h>
 #include <fcntl.h>
 #include <stdlib.h>