diff --git a/lex/Makefile b/lex/Makefile
index a8ac9a7ed..ea6f2be2a 100644
--- a/lex/Makefile
+++ b/lex/Makefile
@@ -18,6 +18,8 @@ include ../config/Makefile
 CAMLRUN ?= ../boot/ocamlrun
 CAMLYACC ?= ../boot/ocamlyacc
 
+ROOTDIR=..
+
 ifeq "$(wildcard $(ROOTDIR)/flexdll/Makefile)" ""
 export OCAML_FLEXLINK:=
 else
@@ -47,7 +49,7 @@ ocamllex.opt: $(OBJS:.cmo=.cmx)
 
 clean::
 	rm -f ocamllex ocamllex.opt
-	rm -f *.cmo *.cmi *.cmx *.cmt *.cmti *.o *~
+	rm -f *.cmo *.cmi *.cmx *.cmt *.cmti *.$(O) *~
 
 parser.ml parser.mli: parser.mly
 	$(CAMLYACC) $(YACCFLAGS) parser.mly
diff --git a/tools/Makefile.shared b/tools/Makefile.shared
index 90096cb33..e86d8273e 100644
--- a/tools/Makefile.shared
+++ b/tools/Makefile.shared
@@ -17,6 +17,14 @@ include ../config/Makefile
 CAMLRUN ?= ../boot/ocamlrun
 CAMLYACC ?= ../boot/ocamlyacc
 
+ROOTDIR=..
+
+ifeq "$(wildcard $(ROOTDIR)/flexdll/Makefile)" ""
+export OCAML_FLEXLINK:=
+else
+export OCAML_FLEXLINK:=$(ROOTDIR)/boot/ocamlrun $(ROOTDIR)/flexdll/flexlink.exe
+endif
+
 CAMLC=$(CAMLRUN) ../boot/ocamlc -nostdlib -I ../boot -use-prims ../byterun/primitives
 CAMLOPT=$(CAMLRUN) ../ocamlopt -nostdlib -I ../stdlib
 CAMLLEX=$(CAMLRUN) ../boot/ocamllex