diff --git a/blog/builder.sh b/blog/builder.sh
index a2054f2..8ab7ac3 100644
--- a/blog/builder.sh
+++ b/blog/builder.sh
@@ -15,4 +15,7 @@ mkdir $out
 cp -r public/$publicPath/* $out/
 
 # Render math in HTML and XML files.
+node $server &
+SERVER_ID=$!
 find $out/ -regex "$out/.*\.html" | xargs ruby $converter
+kill $SERVER_ID
diff --git a/blog/convert.rb b/blog/convert.rb
index 697dc2d..8d5232b 100644
--- a/blog/convert.rb
+++ b/blog/convert.rb
@@ -1,23 +1,24 @@
 require "open3"
 require "nokogiri"
+require "net/http"
+require "json"
 
-def render_cached(cache, command, string, render_comment = nil)
+def render_cached(cache, display, string, render_comment = nil)
   cache.fetch(string) do |new|
     puts "  Rendering #{render_comment || new}"
-    cache[string] = Open3.popen3(command) do |i, o, e, t|
-      i.write new
-      i.close
-      o.read.force_encoding(Encoding::UTF_8).strip
-    end
+    res = Net::HTTP.post URI("http://localhost:3000/render"),
+      { :equations => [ { :str => string, :display => display } ] }.to_json,
+       "Content-Type" => "application/json"
+    cache[string] = JSON.parse(res.body)[0]
   end
 end
 
 def perform_katex_sub(inline_cache, display_cache, content)
   rendered = content.gsub /\\\(((?:[^\\]|\\[^\)])*)\\\)/ do |match|
-    render_cached(inline_cache, "katex", $~[1])
+    render_cached(inline_cache, false, $~[1])
   end
   rendered = rendered.gsub /\$\$((?:[^\$]|$[^\$])*)\$\$/ do |match|
-    render_cached(display_cache, "katex -d", $~[1], "display")
+    render_cached(display_cache, true, $~[1], "display")
   end
   return rendered
 end
diff --git a/blog/default.nix b/blog/default.nix
index dfe5a4d..bb3da43 100644
--- a/blog/default.nix
+++ b/blog/default.nix
@@ -21,7 +21,12 @@ let
     extraFlags = if settings.drafts then " -D " else "";
     builder = ./builder.sh;
     converter = ./convert.rb;
-    buildInputs = [ hugo requiredPackages.katex (ruby.withPackages (ps: [ ps.nokogiri ])) ];
+    server = ./katexserver.js;
+    buildInputs = [
+      hugo
+      requiredPackages.katex requiredPackages.express requiredPackages.bodyParser
+      (ruby.withPackages (ps: [ ps.nokogiri ]))
+    ];
   };
   rev = "b921ddfc8de1282cc82a0d90b2927bf2a5c0ee68";
   sha256 = "1gg7dq9y1hg14qjlj2w1rn0xjgqw58s8kpd5x6c0wfpwszcm87ji";
diff --git a/blog/katexserver.js b/blog/katexserver.js
new file mode 100644
index 0000000..c24814f
--- /dev/null
+++ b/blog/katexserver.js
@@ -0,0 +1,12 @@
+const katex = require('katex');
+const express = require('express');
+const bodyParser = require('body-parser');
+
+app = express();
+app.use(bodyParser.json());
+app.post('/render', (req, res) => {
+    console.log(req.body)
+    res.send(req.body.equations.map(eq =>
+        katex.renderToString(eq.str, { throwOnError: false, displayMode: eq.display })));
+});
+app.listen(3000);
diff --git a/blog/packages.json b/blog/packages.json
index c6b288f..e3fd054 100644
--- a/blog/packages.json
+++ b/blog/packages.json
@@ -1,3 +1,3 @@
 [
-    "katex"
+    "katex", "express", "body-parser"
 ]