diff --git a/interpreter/Makefile b/interpreter/Makefile
index aafdb2b8a8..740554d3a5 100644
--- a/interpreter/Makefile
+++ b/interpreter/Makefile
@@ -213,7 +213,7 @@ opam-release/%:
 		rm -f opam-$*.zip
 		wget https://github.com/WebAssembly/spec/archive/opam-$*.zip
 		cp meta/opam/opam .
-		sed -i "tmp" s/@VERSION/$*/g opam
-		sed -i "tmp" s/@MD5/`md5 -q opam-$*.zip`/g opam
-		rm opam-$*.zip
+		sed -i ".tmp" s/@VERSION/$*/g opam
+		sed -i ".tmp" s/@MD5/`md5 -q opam-$*.zip`/g opam
+		rm opam.tmp opam-$*.zip
 		@echo Created file ./opam, submit to github opam-repository/packages/wasm/wasm.$*/opam
diff --git a/interpreter/meta/opam/opam b/interpreter/meta/opam/opam
index 139251f3fa..845fe675ec 100644
--- a/interpreter/meta/opam/opam
+++ b/interpreter/meta/opam/opam
@@ -14,6 +14,7 @@ depends: [
   "ocamlfind" {build}
   "ocamlbuild" {build}
 ]
+conflicts: ["ocaml-option-bytecode-only"] # uses ocamlopt unconconditionally
 synopsis:
   "Library to read and write WebAssembly (Wasm) files and manipulate their AST"
 url {