diff --git a/tools/tools/nanobsd/dhcpd/common b/tools/tools/nanobsd/dhcpd/common
--- a/tools/tools/nanobsd/dhcpd/common
+++ b/tools/tools/nanobsd/dhcpd/common
@@ -34,6 +34,8 @@
 
 # NB: You want the other file
 
+legacy
+
 NANO_PMAKE="make -j $(sysctl -n hw.ncpu)"
 
 NANO_CFG_BASE=$(pwd)
diff --git a/tools/tools/nanobsd/embedded/common b/tools/tools/nanobsd/embedded/common
--- a/tools/tools/nanobsd/embedded/common
+++ b/tools/tools/nanobsd/embedded/common
@@ -71,6 +71,9 @@
 	echo "NANO_NAME not defined. Use foo.cfg instead."
 fi
 
+# We define our own imaging plan, so instruct nanobsd not to define its own.
+NANO_PLAN=embedded
+
 NANO_SLICE_FAT_SIZE=32m
 NANO_SLICE_CFG_SIZE=32m
 
diff --git a/tools/tools/nanobsd/legacy.sh b/tools/tools/nanobsd/legacy.sh
--- a/tools/tools/nanobsd/legacy.sh
+++ b/tools/tools/nanobsd/legacy.sh
@@ -34,7 +34,13 @@
 # Functions and variable definitions used by the legacy nanobsd
 # image building system.
 
-calculate_partitioning() {
+NANO_PLAN=legacy
+
+# Note: we use the is_defined hack to catch most uses of function redefinition
+# in config files. Older versions of FreeBSD defined these before configs were
+# included, but now we define it after to allow different NANO_PLAN...
+
+is_defined calculate_partitioning || calculate_partitioning() {
 	echo $NANO_MEDIASIZE $NANO_IMAGES \
 		$NANO_SECTS $NANO_HEADS \
 		$NANO_CODESIZE $NANO_CONFSIZE $NANO_DATASIZE |
@@ -92,7 +98,7 @@
 	' > ${NANO_LOG}/_.partitioning
 }
 
-create_code_slice() {
+is_defined create_code_slice || create_code_slice() {
 	pprint 2 "build code slice"
 	pprint 3 "log: ${NANO_OBJ}/_.cs"
 
@@ -145,7 +151,7 @@
 }
 
 
-create_diskimage() {
+is_defined create_diskimage || create_diskimage() {
 	pprint 2 "build diskimage"
 	pprint 3 "log: ${NANO_OBJ}/_.di"
 
diff --git a/tools/tools/nanobsd/nanobsd.sh b/tools/tools/nanobsd/nanobsd.sh
--- a/tools/tools/nanobsd/nanobsd.sh
+++ b/tools/tools/nanobsd/nanobsd.sh
@@ -28,6 +28,18 @@
 
 set -e
 
+legacy() {
+    # Pull in legacy stuff on demand
+    . "${topdir}/legacy.sh"
+}
+
+is_defined() {
+	case $(type $1 2>/dev/null) in
+	*function) return 0 ;;
+	*) return 1 ;;
+	esac
+}
+
 nanobsd_sh=`realpath $0`
 topdir=`dirname ${nanobsd_sh}`
 . "${topdir}/defaults.sh"
@@ -45,9 +57,6 @@
 do_native_xtools=false
 do_prep_image=true
 
-# Pull in legacy stuff for now automatically
-. "${topdir}/legacy.sh"
-
 set +e
 args=`getopt BKXWbc:fhiIknpqvw $*`
 if [ $? -ne 0 ] ; then
@@ -148,6 +157,10 @@
 	usage
 fi
 
+# Transition hack -- If you get this warning, add 'legacy' to your nano config file
+[ -n "$NANO_PLAN" ] || echo "Warning: no plan defined, assuming legacy config."
+[ -n "$NANO_PLAN" ] || legacy
+
 #######################################################################
 # And then it is as simple as that...
 
diff --git a/tools/tools/nanobsd/pcengines/common.conf b/tools/tools/nanobsd/pcengines/common.conf
--- a/tools/tools/nanobsd/pcengines/common.conf
+++ b/tools/tools/nanobsd/pcengines/common.conf
@@ -1,6 +1,8 @@
 #
 #
 
+legacy
+
 NANO_SRC=$(pwd)
 NANO_SRC=${NANO_SRC%/tools/tools/nanobsd/pcengines}
 NANO_OBJ=${NANO_SRC}/../nanobsd-builds/${NANO_NAME}/obj
diff --git a/tools/tools/nanobsd/rescue/common b/tools/tools/nanobsd/rescue/common
--- a/tools/tools/nanobsd/rescue/common
+++ b/tools/tools/nanobsd/rescue/common
@@ -1,5 +1,7 @@
 #!/bin/sh
 
+legacy
+
 #NANO_SRC=$(pwd)
 #NANO_SRC=${NANO_SRC%/tools/tools/nanobsd/rescue}
 #NANO_OBJ=${NANO_SRC}/../nanobsd-builds/${NANO_NAME}/obj