diff --git a/Makefile.inc1 b/Makefile.inc1
index 6db68b627d96..1e992b05c859 100644
--- a/Makefile.inc1
+++ b/Makefile.inc1
@@ -1016,7 +1016,8 @@ _sanity_check: .PHONY .MAKE
 # replacing generated files.  Handle these cases here in an ad-hoc fashion.
 _cleanobj_fast_depend_hack: .PHONY
 	@echo ">>> Deleting stale dependencies...";
-	sh ${.CURDIR}/tools/build/depend-cleanup.sh ${OBJTOP}
+	MACHINE=${MACHINE} MACHINE_ARCH=${MACHINE_ARCH} \
+	    sh ${.CURDIR}/tools/build/depend-cleanup.sh ${OBJTOP}
 
 _worldtmp: .PHONY
 	@echo
diff --git a/tools/build/depend-cleanup.sh b/tools/build/depend-cleanup.sh
index 743da3361cf5..ce962cc1eb86 100755
--- a/tools/build/depend-cleanup.sh
+++ b/tools/build/depend-cleanup.sh
@@ -23,6 +23,16 @@ if [ ! -d "$OBJTOP" ]; then
 	exit 1
 fi
 
+if [ -z "${MACHINE+set}" ]; then
+	echo "$(basename "$0"): MACHINE not set" >&2
+	exit 1
+fi
+
+if [ -z "${MACHINE_ARCH+set}" ]; then
+	echo "$(basename "$0"): MACHINE_ARCH not set" >&2
+	exit 1
+fi
+
 # $1 directory
 # $2 source filename w/o extension
 # $3 source extension