Index: head/Mk/bsd.port.mk
===================================================================
--- head/Mk/bsd.port.mk
+++ head/Mk/bsd.port.mk
@@ -4538,6 +4538,7 @@
 	@cd ${.CURDIR} && ${MAKE} generate-plist
 
 .for _type in EXAMPLES DOCS
+.if !empty(_REALLY_ALL_POSSIBLE_OPTIONS:M${_type})
 .if !target(add-plist-${_type:tl})
 .if defined(PORT${_type}) && !empty(PORT_OPTIONS:M${_type})
 add-plist-${_type:tl}:
@@ -4549,6 +4550,7 @@
 .endfor
 	@${FIND} -P ${PORT${_type}:S/^/${STAGEDIR}${${_type}DIR}\//} ! -type d 2>/dev/null | \
 		${SED} -ne 's,^${STAGEDIR},,p' >> ${TMPPLIST}
+.endif
 .endif
 .endif
 .endfor
Index: head/Mk/bsd.sanity.mk
===================================================================
--- head/Mk/bsd.sanity.mk
+++ head/Mk/bsd.sanity.mk
@@ -162,6 +162,12 @@
 DEV_ERROR+=	"USE_FPC=yes is no longer supported, please use USES=fpc"
 .endif
 
+.for _type in EXAMPLES DOCS
+.  if defined(PORT${_type}) && empty(_REALLY_ALL_POSSIBLE_OPTIONS:M${_type})
+DEV_ERROR+=	"PORT${_type} does not do anything unless the ${_type} option is present."
+.  endif
+.endfor
+
 SANITY_UNSUPPORTED=	USE_OPENAL USE_FAM USE_MAKESELF USE_ZIP USE_LHA USE_CMAKE \
 		USE_READLINE USE_ICONV PERL_CONFIGURE PERL_MODBUILD \
 		USE_PERL5_BUILD USE_PERL5_RUN USE_DISPLAY USE_FUSE \