--- configure.ac.orig	2015-12-21 07:52:02 UTC
+++ configure.ac
@@ -26,7 +26,7 @@ AC_CHECK_LIB([pq], [PQsetdbLogin])
 
 # Checks for header files.
 AC_HEADER_STDC
-AC_CHECK_HEADERS([stdlib.h string.h unistd.h nss.h])
+AC_CHECK_HEADERS([stdlib.h string.h unistd.h nss.h shadow.h])
 
 # Checks for typedefs, structures, and compiler characteristics.
 AC_C_CONST