diff --git a/blog/convert.rb b/blog/convert.rb
index 86461ea..86d660b 100644
--- a/blog/convert.rb
+++ b/blog/convert.rb
@@ -4,7 +4,7 @@ require "nokogiri"
 def perform_katex_sub(content)
   rendered = content.gsub /\\\(((?:[^\\]|\\[^\)])*)\\\)/ do |match|
     puts "  Rendering #{$~[1]}"
-    Open3.popen3("$(npm bin)/katex") do |i, o, e, t|
+    Open3.popen3("katex") do |i, o, e, t|
       i.write $~[1]
       i.close
       o.read.force_encoding(Encoding::UTF_8).strip
@@ -12,7 +12,7 @@ def perform_katex_sub(content)
   end
   rendered = rendered.gsub /\$\$((?:[^\$]|$[^\$])*)\$\$/ do |match|
     puts "  Rendering display."
-    Open3.popen3("$(npm bin)/katex -d") do |i, o, e, t|
+    Open3.popen3("katex -d") do |i, o, e, t|
       i.write $~[1]
       i.close
       o.read.force_encoding(Encoding::UTF_8).strip
diff --git a/blog/default.nix b/blog/default.nix
index 6b88dc6..2a0c431 100644
--- a/blog/default.nix
+++ b/blog/default.nix
@@ -1,9 +1,10 @@
-{ stdenv, hugo, fetchgit, katex, ruby }:
+{ stdenv, hugo, fetchgit, pkgs, nodejs, ruby }:
 
 let
     url = "https://dev.danilafe.com/Web-Projects/blog-static.git";
     rev = "7f3883fb3994f8ae1a64446a88b729662c9244dc";
     sha256 = "065by3rjg7a43dqdl5ib07c0xi86balb5x2l54jqnlh1hz00bd85";
+    requiredPackages = import ./required-packages.nix { inherit pkgs nodejs; };
 in
     stdenv.mkDerivation {
         name = "blog-static";
@@ -13,5 +14,5 @@ in
         };
         builder = ./builder.sh;
         converter = ./convert.rb;
-        buildInputs = [ hugo katex (ruby.withPackages (ps: [ ps.nokogiri ])) ];
+        buildInputs = [ hugo requiredPackages.katex (ruby.withPackages (ps: [ ps.nokogiri ])) ];
     }