diff --git a/configure b/configure
index 5936072f7..467876969 100755
--- a/configure
+++ b/configure
@@ -31,7 +31,8 @@ parser.add_option("--boost",
 
 def pkg_config(pkg, pkgconfig_root):
   env = os.environ.copy()
-  env["PKG_CONFIG_PATH"] = pkgconfig_root
+  if pkgconfig_root:
+    env["PKG_CONFIG_PATH"] = pkgconfig_root
   cmd = subprocess.Popen(['pkg-config', '--static', '--libs', pkg], stdout=subprocess.PIPE, env=env)
   libs, ret = cmd.communicate()
   if (ret): return None
@@ -106,4 +107,4 @@ if __name__ == '__main__':
   config = '\n'.join(map('='.join, config.iteritems())) + '\n'
 
   write('config.mk',
-        '# Do not edit. Generated by the configure script.\n' + config)
\ No newline at end of file
+        '# Do not edit. Generated by the configure script.\n' + config)