diff -r 92b3ce7ca95c configure.ac
--- a/configure.ac	Sat Jul 30 11:36:32 2016 +0200
+++ b/configure.ac	Sun Jul 31 03:21:27 2016 +0800
@@ -3432,6 +3432,13 @@
   [AC_MSG_RESULT(no)
 ])
 
+AC_MSG_CHECKING(for crypt)
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <unistd.h>]], [[void *x=crypt]])],
+  [AC_DEFINE(HAVE_CRYPT, 1, Define if you have the 'crypt' function.)
+   AC_MSG_RESULT(yes)],
+  [AC_MSG_RESULT(no)
+])
+
 AC_MSG_CHECKING(for broken unsetenv)
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
 #include <stdlib.h>
diff -r 92b3ce7ca95c setup.py
--- a/setup.py	Sat Jul 30 11:36:32 2016 +0200
+++ b/setup.py	Sun Jul 31 03:21:27 2016 +0800
@@ -792,11 +792,15 @@
 
         # crypt module.
 
-        if self.compiler.find_library_file(lib_dirs, 'crypt'):
-            libs = ['crypt']
+        if config_h_vars.get('HAVE_CRYPT'):
+            if self.compiler.find_library_file(lib_dirs, 'crypt'):
+                libs = ['crypt']
+            else:
+                libs = []
+            exts.append( Extension('_crypt', ['_cryptmodule.c'],
+                                   libraries=libs) )
         else:
-            libs = []
-        exts.append( Extension('_crypt', ['_cryptmodule.c'], libraries=libs) )
+            missing.append('_crypt')
 
         # CSV files
         exts.append( Extension('_csv', ['_csv.c']) )