I have a problem with including /usr/pkg/include

I wanted to change mail/postfix/Makefile to make it compile the LDAP 
support into postfix. I added the following
	.if defined(POSTFIX_USE_LDAP) && ${POSTFIX_USE_LDAP} == "YES"
	CCARGS+=        -DHAS_LDAP -I${PKGDIR}/include
	AUXLIBS+=       -L${PKGDIR}/lib -lldap -llber
	BUILD_DEFS+=    POSTFIX_USE_LDAP
	.endif

But now, when I try to run
	make POSTFIX_USE_LDAP=YES USE_SASL=YES POSTFIX_USE_TLS=YES update
I get:
	[src/util]
	cc -DHAS_LDAP -DUSE_SASL_AUTH -DHAS_SSL -g -O2 -I/usr/pkg/include -I. 
-DNETBSD1 -c dict_ldap.c
	dict_ldap.c:99: lber.h: No such file or directory
	dict_ldap.c:100: ldap.h: No such file or directory
	*** Error code 1
	
	Stop.

What do I do wrong? The files lber.h and ldap.h _are_ inside 
/usr/pkg/include

Thanks in advance for you help,

Daniel