diff --git a/nix/sources.nix b/nix/sources.nix
index 08fbc1bf..83d461af 100644
--- a/nix/sources.nix
+++ b/nix/sources.nix
@@ -35,13 +35,12 @@ let
 
   fetch_git = name: spec: let
     ref =
-      if spec ? ref
-      then spec.ref
-      else if spec ? branch
+      spec.ref
+      or (if spec ? branch
       then "refs/heads/${spec.branch}"
       else if spec ? tag
       then "refs/tags/${spec.tag}"
-      else abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!";
+      else abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!");
   in
     builtins.fetchGit {
       url = spec.repo;
@@ -175,7 +174,7 @@ let
     inherit (builtins) lessThan nixVersion fetchTarball;
   in
     if lessThan nixVersion "1.12"
-    then fetchTarball ({inherit url;} // (optionalAttrs (!(name == null)) {inherit name;}))
+    then fetchTarball ({inherit url;} // (optionalAttrs (name != null) {inherit name;}))
     else fetchTarball attrs;
 
   # fetchurl version that is compatible between all the versions of Nix
@@ -187,7 +186,7 @@ let
     inherit (builtins) lessThan nixVersion fetchurl;
   in
     if lessThan nixVersion "1.12"
-    then fetchurl ({inherit url;} // (optionalAttrs (!(name == null)) {inherit name;}))
+    then fetchurl ({inherit url;} // (optionalAttrs (name != null) {inherit name;}))
     else fetchurl attrs;
 
   # Create the final "sources" from the config
diff --git a/private b/private
index 80bc1996..7fd92662 160000
--- a/private
+++ b/private
@@ -1 +1 @@
-Subproject commit 80bc1996ca8e0d4b75183f6b76748806511fe6ec
+Subproject commit 7fd92662dbc0af789fc1be44bc64ae2ec3871452