diff --git a/.gitignore b/.gitignore
index fca56579..9f0d9eab 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,4 @@
 *.cmo
 *.annot
 *~
+idl_test_gen.ml
diff --git a/tests/Makefile b/tests/Makefile
index 88f8a447..f49a1959 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -45,5 +45,9 @@ idl_test.cmx: idl_test.ml idl_test.cmi
 	camlp4o $(shell ocamlfind query rpclib.syntax -r -format "-I %d %a" -predicates syntax,preprocessor) $< -printer o > $@.ml
 	$(OCAMLOPT) $(OCAMLFLAGS) -package $(PACKS) -c -o $@ $@.ml
 
+idl_test_gen.ml: idl_test.ml
+	camlp4o $(shell ocamlfind query rpclib.idl -r -format "-I %d %a" -predicates syntax,preprocessor) $< -printer o > $@
+
+
 clean:
 	rm -f *_gen.ml *.annot *.cmx *.cmi *.cmo *.cmxa *.o $(EXECS)