diff --git a/meson.build b/meson.build
index a85fc304..0556b1ed 100644
--- a/meson.build
+++ b/meson.build
@@ -136,6 +136,11 @@ if host_machine.system() != 'netbsd'
     add_project_arguments('-D_POSIX_C_SOURCE=201710L', language: 'c')
 endif
 
+if host_machine.system() == 'darwin'
+    # See https://github.com/ximion/appstream/issues/551
+    add_project_arguments('-D_DARWIN_C_SOURCE', language: 'c')
+endif
+
 if cc.get_id() == 'clang'
     # Clang doesn't understand autofree helpers on GMutexLocker and thinks
     # these variables are irrelevant, so this warning when used with Clang
diff --git a/src/as-system-info.c b/src/as-system-info.c
index 8e5592d4..f0f0c64f 100644
--- a/src/as-system-info.c
+++ b/src/as-system-info.c
@@ -47,12 +47,6 @@
 #include <dirent.h>
 #include <glib.h>
 
-#if defined(__APPLE__)
-typedef unsigned int u_int;
-typedef unsigned char u_char;
-typedef unsigned short u_short;
-#endif
-
 #if defined(__linux__)
 #include <sys/sysinfo.h>
 #elif defined(__FreeBSD__) || defined(__NetBSD__) || defined(__APPLE__)