diff --git a/pkgs/development/compilers/unison/default.nix b/pkgs/development/compilers/unison/default.nix
index d409ec8a276f..025fc8c3fa7d 100644
--- a/pkgs/development/compilers/unison/default.nix
+++ b/pkgs/development/compilers/unison/default.nix
@@ -6,18 +6,18 @@
 
 stdenv.mkDerivation rec {
   pname = "unison-code-manager";
-  milestone_id = "M2g";
+  milestone_id = "M2j";
   version = "1.0.${milestone_id}-alpha";
 
   src = if (stdenv.isDarwin) then
     fetchurl {
       url = "https://github.com/unisonweb/unison/releases/download/release/${milestone_id}/ucm-macos.tar.gz";
-      sha256 = "1ib9pdzrfpzbi35fpwm9ym621nlydplvzgbhnyd86dbwbv3i9sga";
+      sha256 = "0lrj37mfqzwg9n757ymjb440jx51kj1s8g6qv9vis9pxckmy0m08";
     }
   else
     fetchurl {
       url = "https://github.com/unisonweb/unison/releases/download/release/${milestone_id}/ucm-linux.tar.gz";
-      sha256 = "004jx7q657mkcrvilk4lfkp8xcpl2bjflpn9m2p7jzlrlk97v9nj";
+      sha256 = "0qvin1rlkjwijchsijq3vbnn4injawchh2w97kyq7i3idh8ccl59";
     };
 
   # The tarball is just the prebuilt binary, in the archive root.
@@ -31,7 +31,10 @@ stdenv.mkDerivation rec {
   installPhase = ''
     mkdir -p $out/bin
     mv ucm $out/bin
-    wrapProgram $out/bin/ucm --prefix PATH ":" "${lib.makeBinPath [ less ]}";
+    mv ui $out/ui
+    wrapProgram $out/bin/ucm \
+      --prefix PATH ":" "${lib.makeBinPath [ less ]}" \
+      --set UCM_WEB_UI "$out/ui"
   '';
 
   meta = with lib; {