diff --git a/configure.in b/configure.in
index d38b0fabb..67d1c2a89 100644
--- a/configure.in
+++ b/configure.in
@@ -579,7 +579,22 @@ fi
 if test x$fast = xtrue; then
 	AC_HAVE_LIBRARY([neo_cgi],[LIBS="$LIBS"],[AC_MSG_ERROR([ClearSilver library neo_cgi not found!])])
 	AC_HAVE_LIBRARY([neo_utl],[LIBS="$LIBS"],[AC_MSG_ERROR([ClearSilver library neo_utl not found!])])
-	AC_HAVE_LIBRARY([z],[LIBS="$LIBS"],[AC_MSG_ERROR([ClearSilver dependency zlib not found!])])
+	AC_MSG_CHECKING([ClearSilver requires zlib])
+	saved_CFLAGS=$CFLAGS
+	saved_LIBS=$LIBS
+	LIBS="-lneo_cgi -lneo_cs -lneo_utl"
+	CFLAGS="-I/usr/include/ClearSilver"
+	AC_TRY_LINK(
+		[#include <ClearSilver.h>],
+		[
+			NEOERR *err = cgi_display(NULL, NULL);
+		],
+		[AC_MSG_RESULT([no]); clearsilver_LIBS="$LIBS"],
+		[AC_MSG_RESULT([yes]); clearsilver_LIBS="$LIBS -lz"]
+	)
+	AC_SUBST(clearsilver_LIBS)
+	LIBS=$saved_LIBS
+	CFLAGS=$saved_CFLAGS
 dnl autoconf does not like CamelCase!? How to fix this?
 dnl	AC_CHECK_HEADER([ClearSilver/ClearSilver.h],,[AC_MSG_ERROR([ClearSilver header file ClearSilver/ClearSilver.h not found!])])
 
diff --git a/src/libfast/Makefile.am b/src/libfast/Makefile.am
index 575a06b73..35d102109 100644
--- a/src/libfast/Makefile.am
+++ b/src/libfast/Makefile.am
@@ -3,6 +3,6 @@ ipseclib_LTLIBRARIES = libfast.la
 libfast_la_SOURCES = context.h dispatcher.c request.h session.h \
   controller.h dispatcher.h request.c session.c filter.h smtp.c smtp.h
 libfast_la_LIBADD = $(top_builddir)/src/libstrongswan/libstrongswan.la \
-  -lfcgi -lneo_cgi -lneo_cs -lneo_utl -lz $(PTHREADLIB)
+  -lfcgi $(clearsilver_LIBS) $(PTHREADLIB)
 INCLUDES = -I$(top_srcdir)/src/libstrongswan -I/usr/include/ClearSilver
 AM_CFLAGS = -rdynamic