diff --git a/configure.ac b/configure.ac
index f03283b3..8e90bdd7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -67,7 +67,7 @@ LDFLAGS="$LDFLAGS -L$nix/lib/nix"
 
 AC_CHECK_HEADER([store-api.hh], [:],
   [AC_MSG_ERROR([Nix headers not found; please install Nix or check the `--with-nix' option.])])
-AC_CHECK_LIB([expr], [_ZN3nix9EvalState17parseExprFromFileERKSs], [:],
+AC_CHECK_LIB([expr], [_ZN3nix9EvalState8evalFileERKSsRNS_5ValueE], [:],
   [AC_MSG_ERROR([Nix library not found; please install Nix or check the `--with-nix' option.])])
 
 CPPFLAGS="$old_CPPFLAGS"
diff --git a/release.nix b/release.nix
index e5603dcb..868ba424 100644
--- a/release.nix
+++ b/release.nix
@@ -34,7 +34,7 @@ in rec {
       '';
 
       configureFlags =
-        [ "--with-nix=${nix}"
+        [ "--with-nix=${nixUnstable}"
           "--with-docbook-xsl=${docbook_xsl}/xml/xsl/docbook"
         ];
 
diff --git a/src/c/hydra-eval-jobs.cc b/src/c/hydra-eval-jobs.cc
index 7680a6d3..7da8ad56 100644
--- a/src/c/hydra-eval-jobs.cc
+++ b/src/c/hydra-eval-jobs.cc
@@ -284,9 +284,8 @@ void run(Strings args)
 
     store = openStore();
 
-    Expr * e = state.parseExprFromFile(releaseExpr);
     Value v;
-    state.mkThunk_(v, e);
+    state.evalFile(releaseExpr, v);
 
     XMLWriter doc(true, std::cout);
     XMLOpenElement root(doc, "jobs");