diff --git a/pypy/module/crypt/interp_crypt.py b/pypy/module/crypt/interp_crypt.py

index d227b6a..da969e6 100644

--- a/pypy/module/crypt/interp_crypt.py

+++ b/pypy/module/crypt/interp_crypt.py

@@ -6,7 +6,7 @@ import sys

 if sys.platform.startswith('darwin'):

     eci = ExternalCompilationInfo()

 else:

-    eci = ExternalCompilationInfo(libraries=['crypt'])

+    eci = ExternalCompilationInfo(libraries=['crypt'], includes=['crypt.h'])

 c_crypt = rffi.llexternal('crypt', [rffi.CCHARP, rffi.CCHARP], rffi.CCHARP,

                           compilation_info=eci, releasegil=False)