diff --git a/packages/genodelabs/default.nix b/packages/genodelabs/default.nix
index 459d73b..b21a1d5 100644
--- a/packages/genodelabs/default.nix
+++ b/packages/genodelabs/default.nix
@@ -40,7 +40,16 @@ let
       substituteInPlace tool/check_abi \
         --replace "exec nm" "exec ${toolPrefix}nm"
     '';
-    dontBuild = true;
+
+    buildPhase = ''
+      echo { >> ports.nix
+      find repos/*/ports -name '*.hash' | while read hashFile
+      do
+        echo "  $(basename --suffix=.hash $hashFile) = \"$(cut -c -6 $hashFile)\";" >> ports.nix
+      done
+      echo } >> ports.nix
+    '';
+
     installPhase = "cp -a . $out";
   };
 
@@ -53,12 +62,13 @@ let
     { hash ? "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA="
     , patches ? [ ], ... }@args:
     let havePatches = patches != [ ];
+      version = builtins.getAttr name (import "${genodeSources}/ports.nix");
     in stdenvNoCC.mkDerivation (args // {
+      name = name + "-port-" + version;
+      inherit version patches;
+      preferLocalBuild = true;
       outputHashMode = "recursive";
       outputHash = hash;
-      pname = name;
-      inherit (genodeSources) version;
-      inherit patches;
 
       GIT_SSL_CAINFO = "${cacert}/etc/ssl/certs/ca-bundle.crt";
       VERBOSE = "";
@@ -83,7 +93,7 @@ let
           export CONTRIB_DIR=$NIX_BUILD_TOP/contrib
           export GENODE_DIR=${if havePatches then "$(pwd)" else genodeSources}
           mkdir $CONTRIB_DIR
-          $GENODE_DIR/tool/ports/prepare_port $pname CHECK_HASH=no
+          $GENODE_DIR/tool/ports/prepare_port ${name} CHECK_HASH=no
           runHook postBuild
         '';
 
@@ -96,6 +106,7 @@ let
           find $CONTRIB_DIR/* -name .svn -exec rm -rf {} \; || true
           find $CONTRIB_DIR/* -name '*.t?z' -exec rm -rf {} \; || true
           find $CONTRIB_DIR/* -name '*.tar.*' -exec rm -rf {} \; || true
+          find $CONTRIB_DIR/* -name '*.zip' -exec rm -rf {} \; || true
 
           mkdir $out
           cp -a $CONTRIB_DIR/* $out/