diff --git a/otherlibs/labltk/example/Makefile b/otherlibs/labltk/example/Makefile
index 0f5f72ae0..c485b407e 100644
--- a/otherlibs/labltk/example/Makefile
+++ b/otherlibs/labltk/example/Makefile
@@ -4,7 +4,7 @@ COMPFLAGS=-I ../lib -I ../support
 
 all: hello demo eyes calc clock tetris
 
-opt: hello.opt demo.opt eyes.opt calc.opt tetris.opt
+opt: hello.opt demo.opt eyes.opt calc.opt clock.opt tetris.opt
 
 hello: hello.cmo
 	$(LABLC) -custom $(COMPFLAGS) -o hello tk41.cma hello.cmo $(TKLINKOPT)
@@ -23,8 +23,9 @@ clock: clock.cmo
 	      $(TKLINKOPT) -cclib -lunix
 
 clock.opt: clock.cmx
-	$(CAMLOPT) $(COMPFLAGS) -o clock.opt tk41.cmxa unix.cmxa clock.cmx \
-	      $(TKLINKOPT) -cclib -lunix
+	$(CAMLOPT) $(COMPFLAGS) -o clock.opt \
+	      tk41.cmxa -I $(OTHERS)/unix unix.cmxa clock.cmx \
+	      $(TKLINKOPT) -cclib "-L$(OTHERS)/unix -lunix"
 
 tetris: tetris.cmo
 	$(LABLC) -custom $(COMPFLAGS) -o tetris tk41.cma tetris.cmo $(TKLINKOPT)
@@ -45,4 +46,4 @@ clean:
 	$(CAMLOPT) -c $(COMPFLAGS) $<
 
 .cmx.opt:
-	labltkopt $(COMPFLAGS) -o $@ $<
+	$(CAMLOPT) $(COMPFLAGS) -o $@ tk41.cmxa $< $(TKLINKOPT)