1 files changed, 6 insertions, 0 deletions
diff --git a/nixpkgs/pkgs/development/beam-modules/build-mix.nix b/nixpkgs/pkgs/development/beam-modules/build-mix.nix
index f74da7b7827d..4c5ad3f6fa24 100644
--- a/nixpkgs/pkgs/development/beam-modules/build-mix.nix
+++ b/nixpkgs/pkgs/development/beam-modules/build-mix.nix
@@ -87,6 +87,12 @@ let
         fi
       done
 
+      # Copy the source so it can be used by dependent packages. For example,
+      # phoenix applications need the source of phoenix and phoenix_html to
+      # build javascript and css assets.
+      mkdir -p $out/src
+      cp -r $src/* "$out/src"
+
       runHook postInstall
     '';