diff --git a/setup.py b/setup.py
index 270651d4e..1888a9b12 100644
--- a/setup.py
+++ b/setup.py
@@ -37,7 +37,10 @@ _LIB_IMAGING = (
 
 
 def _add_directory(path, dir, where=None):
-    if dir and os.path.isdir(dir) and dir not in path:
+    if dir is None:
+        return
+    dir = os.path.realpath(dir)
+    if os.path.isdir(dir) and dir not in path:
         if where is None:
             path.append(dir)
         else:
@@ -156,6 +159,30 @@ class pil_build_ext(build_ext):
             _add_directory(library_dirs, lib_root)
             _add_directory(include_dirs, include_root)
 
+        # respect CFLAGS/LDFLAGS
+        for k in ('CFLAGS', 'LDFLAGS'):
+            if k in os.environ:
+                for match in re.finditer(r'-I([^\s]+)', os.environ[k]):
+                    _add_directory(include_dirs, match.group(1))
+                for match in re.finditer(r'-L([^\s]+)', os.environ[k]):
+                    _add_directory(library_dirs, match.group(1))
+
+        # include, rpath, if set as environment variables:
+        for k in ('C_INCLUDE_PATH', 'CPATH', 'INCLUDE'):
+            if k in os.environ:
+                for d in os.environ[k].split(os.path.pathsep):
+                    _add_directory(include_dirs, d)
+
+        for k in ('LD_RUN_PATH', 'LIBRARY_PATH', 'LIB'):
+            if k in os.environ:
+                for d in os.environ[k].split(os.path.pathsep):
+                    _add_directory(library_dirs, d)
+
+        prefix = sysconfig.get_config_var("prefix")
+        if prefix:
+            _add_directory(library_dirs, os.path.join(prefix, "lib"))
+            _add_directory(include_dirs, os.path.join(prefix, "include"))
+
         #
         # add platform directories
 
@@ -187,7 +214,7 @@ class pil_build_ext(build_ext):
                     _add_directory(include_dirs, os.path.join(prefix, 'include'))
             except:
                 pass # homebrew not installed
-                    
+
         elif sys.platform.startswith("linux"):
             for platform_ in (plat.processor(), plat.architecture()[0]):
 
@@ -215,33 +242,8 @@ class pil_build_ext(build_ext):
                     _add_directory(library_dirs, "/usr/pkg/lib")
                     _add_directory(include_dirs, "/usr/pkg/include")
 
-        _add_directory(library_dirs, "/usr/local/lib")
         # FIXME: check /opt/stuff directories here?
 
-        # respect CFLAGS/LDFLAGS
-        for k in ('CFLAGS', 'LDFLAGS'):
-            if k in os.environ:
-                for match in re.finditer(r'-I([^\s]+)', os.environ[k]):
-                    _add_directory(include_dirs, match.group(1))
-                for match in re.finditer(r'-L([^\s]+)', os.environ[k]):
-                    _add_directory(library_dirs, match.group(1))
-
-        # include, rpath, if set as environment variables:
-        for k in ('C_INCLUDE_PATH', 'INCLUDE'):
-            if k in os.environ:
-                for d in os.environ[k].split(os.path.pathsep):
-                    _add_directory(include_dirs, d)
-
-        for k in ('LD_RUN_PATH', 'LIBRARY_PATH', 'LIB'):
-            if k in os.environ:
-                for d in os.environ[k].split(os.path.pathsep):
-                    _add_directory(library_dirs, d)
-
-        prefix = sysconfig.get_config_var("prefix")
-        if prefix:
-            _add_directory(library_dirs, os.path.join(prefix, "lib"))
-            _add_directory(include_dirs, os.path.join(prefix, "include"))
-
         #
         # locate tkinter libraries