diff --git a/build/cmake/setup.cmake b/build/cmake/setup.cmake
index 5c0fd0e1c9..17a68b2f15 100644
--- a/build/cmake/setup.cmake
+++ b/build/cmake/setup.cmake
@@ -45,6 +45,9 @@ endif()
 if(UNIX)
     wx_setup_definition(wxUSE_UNIX)
     wx_setup_definition(__UNIX__)
+endif()
+
+if(UNIX AND NOT APPLE)
     wx_setup_definition(_GNU_SOURCE)
 endif()