diff -r e0bd083fc9c1 Lib/distutils/unixccompiler.py
--- a/Lib/distutils/unixccompiler.py	Sun Apr 19 21:12:14 2015 +0200
+++ b/Lib/distutils/unixccompiler.py	Mon Apr 20 15:48:55 2015 +0900
@@ -79,6 +79,7 @@
     static_lib_format = shared_lib_format = dylib_lib_format = "lib%s%s"
     if sys.platform == "cygwin":
         exe_extension = ".exe"
+        dylib_lib_extension = ".dll.a"
 
     def preprocess(self, source, output_file=None, macros=None,
                    include_dirs=None, extra_preargs=None, extra_postargs=None):