diff --git a/setup.py b/setup.py
index bbf6530f1..e756236fa 100644
--- a/setup.py
+++ b/setup.py
@@ -111,8 +111,8 @@ class pil_build_ext(build_ext):
             _add_directory(library_dirs, "/opt/local/lib")
             _add_directory(include_dirs, "/opt/local/include")
             # freetype2 ships with X11
-            _add_directory(library_dirs, "/usr/x11/lib")
-            _add_directory(include_dirs, "/usr/x11/include")
+            _add_directory(library_dirs, "/usr/X11/lib")
+            _add_directory(include_dirs, "/usr/X11/include")
 
         elif sys.platform.startswith("linux"):
             if platform.processor() == "x86_64":