diff --git a/Makefile b/Makefile
index baff88d..b6c5824 100644
--- a/Makefile
+++ b/Makefile
@@ -9,7 +9,7 @@ all: $(COQMAKEFILE)
 
 clean:
 	-$(MAKE) -f $(COQMAKEFILE) clean
-	rm -f $(COQMAKEFILE)
+	rm -f $(COQMAKEFILE)*
 
 $(COQMAKEFILE): Makefile _CoqProject
 	$(COQBIN)coq_makefile -f _CoqProject -o Makefile.coq
diff --git a/opam b/opam
index e4222d8..22ff524 100644
--- a/opam
+++ b/opam
@@ -12,7 +12,7 @@ build: [make "-j%{jobs}%"]
 install: [make "install"]
 depends: [
   "ocaml"
-  "coq" { >= "8.17" | = "dev" }
+  "coq" { ( >= "8.17" & < "8.18~" ) | = "dev" }
 ]
 synopsis: "Smpl: An Extensible Tactic for Coq"
 description: """