diff --git a/meson.build b/meson.build
index a89ca55cd..be526768e 100644
--- a/meson.build
+++ b/meson.build
@@ -1781,11 +1781,17 @@ have_sh = find_program('sh', required : false).found() # For glib-gettextize
 # FIXME: defines in config.h that are not actually used anywhere
 # (we add them for now to minimise the diff)
 glib_conf.set('HAVE_DLFCN_H', 1)
-glib_conf.set('__EXTENSIONS__', 1)
 glib_conf.set('STDC_HEADERS', 1)
 # THREADS_NONE
 glib_conf.set('SIZEOF___INT64', 8)
 
+# FIXME: How to detect Solaris? https://github.com/mesonbuild/meson/issues/1578
+if host_system == 'sunos'
+  glib_conf.set('_XOPEN_SOURCE_EXTENDED', 1)
+  glib_conf.set('_XOPEN_SOURCE', 2)
+  glib_conf.set('__EXTENSIONS__',1)
+endif
+
 glib_conf.set('GIO_MODULE_DIR', glib_giomodulesdir)
 
 # Sadly Meson does not expose this value: