diff --git a/Makefile.inc1 b/Makefile.inc1
--- a/Makefile.inc1
+++ b/Makefile.inc1
@@ -1082,7 +1082,7 @@
 _cleanobj_fast_depend_hack: .PHONY
 	@echo ">>> Deleting stale dependencies...";
 	MACHINE=${MACHINE} MACHINE_ARCH=${MACHINE_ARCH} \
-	    ALL_libcompats=${_ALL_libcompats:Q} \
+	    ALL_libcompats=${_ALL_libcompats:Q} MAKE=${MAKE} \
 	    sh ${.CURDIR}/tools/build/depend-cleanup.sh ${OBJTOP} ${SRCTOP}
 
 _cleanworldtmp: .PHONY
@@ -1177,7 +1177,7 @@
 .endfor
 .else
 	${_+_}cd ${.CURDIR}; env CLEANMK="_NO_INCLUDE_COMPILERMK=t ${CLEANDIR}" \
-	    MAKE=${MAKE} ${WMAKE} _cleanobj_fast_depend_hack
+	    ${WMAKE} _cleanobj_fast_depend_hack
 .endif	# ${MK_CLEAN} == "yes"
 _obj:
 	@echo
diff --git a/tools/build/depend-cleanup.sh b/tools/build/depend-cleanup.sh
--- a/tools/build/depend-cleanup.sh
+++ b/tools/build/depend-cleanup.sh
@@ -124,10 +124,8 @@
 fi
 
 : ${CLEANMK=""}
-if [ -n "$CLEANMK" ]; then
-	if [ -z "${MAKE+set}" ]; then
-		err "MAKE not set"
-	fi
+if [ -z "${MAKE+set}" ]; then
+	err "MAKE not set"
 fi
 
 if [ -z "${MACHINE+set}" ]; then
@@ -176,9 +174,37 @@
 	awk 'int($1) > 0 { epoch = $1 } END { print epoch }' "$1"
 }
 
+# Regular expression matching the names of src.conf(5) options which
+# don't affect the build.
+#
+# This filter is applied to both the current options and the cached
+# options so we don't force a rebuild just because the filter itself
+# changed.
+IGNORED_OPTS='CLEAN|EXAMPLES|MAN|TESTS|WARNS|WERROR|INSTALL.*|STAGING.*'
+
+extract_src_opts()
+{
+	$MAKE -C "$SRCTOP" -f "$SRCTOP"/Makefile.inc1 \
+	    -V $'SRC_OPT_LIST:O:ts\n' |
+	egrep -v "^WITH(OUT)?_(${IGNORED_OPTS})="
+}
+
+extract_obj_opts()
+{
+	for fn; do
+		if [ -f "${fn}" ]; then
+			cat "${fn}"
+		else
+			echo "# ${fn}"
+		fi
+	done |
+	egrep -v "^WITH(OUT)?_(${IGNORED_OPTS})="
+}
+
 clean_world()
 {
 	local buildepoch="$1"
+	local srcopts="$2"
 
 	# The caller may set CLEANMK in the environment to make target(s) that
 	# should be invoked instead of just destroying everything.  This is
@@ -201,19 +227,26 @@
 
 	mkdir -p "$OBJTOP"
 	echo "$buildepoch" > "$OBJTOP"/.clean_build_epoch
+	echo "$srcopts" > "$OBJTOP"/.src_opts
 
 	exit 0
 }
 
-check_epoch()
+check_epoch_and_opts()
 {
 	local srcepoch objepoch
+	local srcopts objopts
 
 	srcepoch=$(extract_epoch "$SRCTOP"/.clean_build_epoch)
 	if [ -z "$srcepoch" ]; then
 		err "Malformed .clean_build_epoch; please validate the last line"
 	fi
 
+	srcopts=$(extract_src_opts)
+	if [ -z "$srcopts" ]; then
+		err "Unable to extract source options"
+	fi
+
 	# We don't discriminate between the varying degrees of difference
 	# between epochs.  If it went backwards we could be bisecting across
 	# epochs, in which case the original need to clean likely still stands.
@@ -223,12 +256,22 @@
 			echo "Cleaning - src epoch: $srcepoch, objdir epoch: ${objepoch:-unknown}"
 		fi
 
-		clean_world "$srcepoch"
+		clean_world "$srcepoch" "$srcopts"
+		# NORETURN
+	fi
+
+	objopts=$(extract_obj_opts "$OBJTOP"/.src_opts)
+	if [ "$srcopts" != "$objopts" ]; then
+		if [ "$VERBOSE" ]; then
+			echo "Cleaning - build options have changed"
+		fi
+
+		clean_world "$srcepoch" "$srcopts"
 		# NORETURN
 	fi
 }
 
-check_epoch
+check_epoch_and_opts
 
 #### Typical dependency cleanup begins here.