diff --git a/pkgs/development/tools/ocaml/findlib/default.nix b/pkgs/development/tools/ocaml/findlib/default.nix
index 7d95963209a3..4398d8e41881 100644
--- a/pkgs/development/tools/ocaml/findlib/default.nix
+++ b/pkgs/development/tools/ocaml/findlib/default.nix
@@ -38,7 +38,7 @@ stdenv.mkDerivation rec {
             export CAML_LD_LIBRARY_PATH="''${CAML_LD_LIBRARY_PATH}''${CAML_LD_LIBRARY_PATH:+:}''$1/lib/ocaml/${ocaml.version}/site-lib/stublibs"
         fi
         export OCAMLFIND_DESTDIR="''$out/lib/ocaml/${ocaml.version}/site-lib/"
-        if test -n "$createFindlibDestdir"; then
+        if test -n "''${createFindlibDestdir-}"; then
           mkdir -p $OCAMLFIND_DESTDIR
         fi
     }