diff --git a/setup.py b/setup.py
index 5c1b3e705..a250c2d9c 100755
--- a/setup.py
+++ b/setup.py
@@ -370,7 +370,7 @@ class pil_build_ext(build_ext):
 
                 for platform_ in arch_tp:
                     dirs = libdirs.get(platform_, None)
-                    if not platform_:
+                    if not dirs:
                         continue
                     for path in dirs:
                         _add_directory(library_dirs, path)