--- mp-5.2.1/makefile.in
+++ mp-5.2.1/makefile.in
@@ -4,7 +4,7 @@ all: $(APPNAME) docs build-mo
 
 PROJ=mp
 
-ADD_DOCS=AUTHORS README COPYING RELEASE_NOTES \
+ADD_DOCS=AUTHORS README RELEASE_NOTES \
 	mp_templates.sample doc/mp_function_reference.html
 GRUTATXT_DOCS=doc/mp_index.html doc/mp_cookbook.html doc/mp_internals.html \
 	doc/mp_configuration.html doc/mp_data_model.html \
@@ -26,10 +26,10 @@ version:
 	$(CC) $(CFLAGS) -I. `cat config.cflags` -c $<
 
 $(MPDM)/libmpdm.a:
-	( cd $(MPDM); $(MAKE) )
+	$(MAKE) -C $(MPDM)
 
 $(MPSL)/libmpsl.a: $(MPDM)/libmpdm.a
-	( cd $(MPSL); $(MAKE) )
+	$(MAKE) -C $(MPSL)
 
 dep:
 	gcc -MM *.c `cat config.cflags` > makefile.depend
@@ -88,8 +88,8 @@ $(APPNAME).1: doc/mp_man.txt
 	grutatxt -m man -t "Minimum Profit" < doc/mp_man.txt > $(APPNAME).1
 
 docs: $(DOCS)
-	(cd $(MPDM); $(MAKE) docs)
-	(cd $(MPSL); $(MAKE) docs)
+	$(MAKE) -C $(MPDM) docs
+	$(MAKE) -C $(MPSL) docs
 
 distcopy: distclean docs
 	mkdir -p $(DIST_TARGET) ; \
@@ -134,8 +134,8 @@ install: $(INSTALL_MSG) installdoc install-mo
 
 installdoc:
 	./mkinstalldirs $(PREFIX)/share/doc/$(APPNAME)
-	( cd $(MPDM); $(MAKE) installdoc )
-	( cd $(MPSL); $(MAKE) installdoc )
+	$(MAKE) -C $(MPDM) installdoc
+	$(MAKE) -C $(MPSL) installdoc
 	install -m 644 doc/* $(PREFIX)/share/doc/$(APPNAME)
 	install -m 644 $(ADD_DOCS) $(PREFIX)/share/doc/$(APPNAME)
 	[ -f doc/mp_index.html ] && install -m 644 doc/mp_index.html $(PREFIX)/share/doc/$(APPNAME)/index.html || true