diff --git a/libpkgconf/client.c b/libpkgconf/client.c
index 4ddc13d..139098c 100644
--- a/libpkgconf/client.c
+++ b/libpkgconf/client.c
@@ -56,8 +56,13 @@ pkgconf_client_init(pkgconf_client_t *client, pkgconf_error_handler_func_t error
 
 	pkgconf_path_build_from_environ("PKG_CONFIG_SYSTEM_LIBRARY_PATH", SYSTEM_LIBDIR, &client->filter_libdirs);
 	pkgconf_path_build_from_environ("PKG_CONFIG_SYSTEM_INCLUDE_PATH", SYSTEM_INCLUDEDIR, &client->filter_includedirs);
+
+	/* GCC uses these environment variables to define system include paths, so we should check them. */
+	pkgconf_path_build_from_environ("LIBRARY_PATH", NULL, &client->filter_libdirs);
+	pkgconf_path_build_from_environ("CPATH", NULL, &client->filter_includedirs);
 	pkgconf_path_build_from_environ("C_INCLUDE_PATH", NULL, &client->filter_includedirs);
 	pkgconf_path_build_from_environ("CPLUS_INCLUDE_PATH", NULL, &client->filter_includedirs);
+	pkgconf_path_build_from_environ("OBJC_INCLUDE_PATH", NULL, &client->filter_includedirs);
 }
 
 /*