--- a/ext/rugged/extconf.rb
+++ b/ext/rugged/extconf.rb
@@ -44,7 +44,7 @@
 
   major = minor = nil
 
-  File.readlines(File.join(LIBGIT2_DIR, "include", "git2", "version.h")).each do |line|
+  File.readlines(File.join("/usr", "include", "git2", "version.h")).each do |line|
     if !major && (matches = line.match(/^#define LIBGIT2_VER_MAJOR ([0-9]+)$/))
       major = matches[1]
       next
