diff --git a/pkgs/development/tools/ocaml/jbuilder/default.nix b/pkgs/development/tools/ocaml/jbuilder/default.nix
index d48bc4101113..38fd4323d5ca 100644
--- a/pkgs/development/tools/ocaml/jbuilder/default.nix
+++ b/pkgs/development/tools/ocaml/jbuilder/default.nix
@@ -2,16 +2,18 @@
 
 stdenv.mkDerivation rec {
   name = "jbuilder-${version}";
-  version = "1.0+beta17";
+  version = "1.0+beta20";
   src = fetchFromGitHub {
     owner = "ocaml";
     repo = "dune";
     rev = "${version}";
-    sha256 = "04pyry459hp2r2s9m5xkcq1glzp20ddz5wb1w8nzp3zgygy0431x";
+    sha256 = "0571lzm8caq6wnia7imgy4a27x5l2bvxiflg0jrwwml0ylnii65f";
   };
 
   buildInputs = [ ocaml ];
 
+  dontAddPrefix = true;
+
   installPhase = "${opam}/bin/opam-installer -i --prefix=$out --libdir=$OCAMLFIND_DESTDIR";
 
   preFixup = "rm -rf $out/jbuilder";