diff --git a/Lib/distutils/command/build_ext.py b/Lib/distutils/command/build_ext.py
index 70e8a73455c..936a5f633a1 100644
--- a/Lib/distutils/command/build_ext.py
+++ b/Lib/distutils/command/build_ext.py
@@ -149,6 +149,8 @@ class build_ext (Command):
             self.libraries = []
         if self.library_dirs is None:
             self.library_dirs = []
+        elif type(self.library_dirs) is StringType:
+            self.library_dirs = string.split(self.library_dirs, os.pathsep)
         if self.rpath is None:
             self.rpath = []