diff -rU3 pkg-config-0.29.1/pkg.c pkg-config-0.29.1.new/pkg.c
--- pkg-config-0.29.1/pkg.c	2016-02-26 17:56:52.000000000 +0100
+++ pkg-config-0.29.1.new/pkg.c	2016-12-29 14:35:51.940067584 +0100
@@ -808,6 +808,12 @@
 
   system_directories = add_env_variable_to_list (system_directories, search_path);
 
+  search_path = g_getenv ("CPATH");
+  if (search_path != NULL)
+    {
+      system_directories = add_env_variable_to_list (system_directories, search_path);
+    }
+
   search_path = g_getenv ("C_INCLUDE_PATH");
   if (search_path != NULL)
     {