diff --git a/src/library/entry.cr b/src/library/entry.cr
index d592e43..0a08246 100644
--- a/src/library/entry.cr
+++ b/src/library/entry.cr
@@ -46,17 +46,19 @@ class Entry
     file.close
   end
 
-  def build_json(json : JSON::Builder, *, slim = false)
-    json.object do
-      {% for str in ["zip_path", "title", "size", "id"] %}
+  def build_json(*, slim = false)
+    JSON.build do |json|
+      json.object do
+        {% for str in ["zip_path", "title", "size", "id"] %}
         json.field {{str}}, @{{str.id}}
       {% end %}
-      json.field "title_id", @book.id
-      json.field "pages" { json.number @pages }
-      unless slim
-        json.field "display_name", @book.display_name @title
-        json.field "cover_url", cover_url
-        json.field "mtime" { json.number @mtime.to_unix }
+        json.field "title_id", @book.id
+        json.field "pages" { json.number @pages }
+        unless slim
+          json.field "display_name", @book.display_name @title
+          json.field "cover_url", cover_url
+          json.field "mtime" { json.number @mtime.to_unix }
+        end
       end
     end
   end
diff --git a/src/library/library.cr b/src/library/library.cr
index 06b1e0f..508a274 100644
--- a/src/library/library.cr
+++ b/src/library/library.cr
@@ -65,16 +65,15 @@ class Library
     titles.flat_map &.deep_entries
   end
 
-  def build_json(json : JSON::Builder, *, slim = false, shallow = false)
-    json.object do
-      json.field "dir", @dir
-      json.field "titles" do
-        json.array do
-          self.titles.each do |title|
-            raw = JSON.build do |j|
-              title.build_json j, slim: slim, shallow: shallow
+  def build_json(*, slim = false, shallow = false)
+    JSON.build do |json|
+      json.object do
+        json.field "dir", @dir
+        json.field "titles" do
+          json.array do
+            self.titles.each do |title|
+              json.raw title.build_json(slim: slim, shallow: shallow)
             end
-            json.raw raw
           end
         end
       end
diff --git a/src/library/title.cr b/src/library/title.cr
index 0b91603..957a608 100644
--- a/src/library/title.cr
+++ b/src/library/title.cr
@@ -65,51 +65,47 @@ class Title
 
   alias SortContext = NamedTuple(username: String, opt: SortOptions)
 
-  def build_json(json : JSON::Builder, *, slim = false, shallow = false,
+  def build_json(*, slim = false, shallow = false,
                  sort_context : SortContext? = nil)
-    json.object do
-      {% for str in ["dir", "title", "id"] %}
+    JSON.build do |json|
+      json.object do
+        {% for str in ["dir", "title", "id"] %}
         json.field {{str}}, @{{str.id}}
       {% end %}
-      json.field "signature" { json.number @signature }
-      unless slim
-        json.field "display_name", display_name
-        json.field "cover_url", cover_url
-        json.field "mtime" { json.number @mtime.to_unix }
-      end
-      unless shallow
-        json.field "titles" do
-          json.array do
-            self.titles.each do |title|
-              raw = JSON.build do |j|
-                title.build_json j, slim: slim, shallow: shallow
+        json.field "signature" { json.number @signature }
+        unless slim
+          json.field "display_name", display_name
+          json.field "cover_url", cover_url
+          json.field "mtime" { json.number @mtime.to_unix }
+        end
+        unless shallow
+          json.field "titles" do
+            json.array do
+              self.titles.each do |title|
+                json.raw title.build_json(slim: slim, shallow: shallow)
               end
-              json.raw raw
             end
           end
-        end
-        json.field "entries" do
-          json.array do
-            _entries = if sort_context
-                         sorted_entries sort_context[:username],
-                           sort_context[:opt]
-                       else
-                         @entries
-                       end
-            _entries.each do |entry|
-              raw = JSON.build do |j|
-                entry.build_json j, slim: slim
+          json.field "entries" do
+            json.array do
+              _entries = if sort_context
+                           sorted_entries sort_context[:username],
+                             sort_context[:opt]
+                         else
+                           @entries
+                         end
+              _entries.each do |entry|
+                json.raw entry.build_json(slim: slim)
               end
-              json.raw raw
             end
           end
-        end
-        json.field "parents" do
-          json.array do
-            self.parents.each do |title|
-              json.object do
-                json.field "title", title.title
-                json.field "id", title.id
+          json.field "parents" do
+            json.array do
+              self.parents.each do |title|
+                json.object do
+                  json.field "title", title.title
+                  json.field "id", title.id
+                end
               end
             end
           end
diff --git a/src/routes/api.cr b/src/routes/api.cr
index 3dc878e..8c66e13 100644
--- a/src/routes/api.cr
+++ b/src/routes/api.cr
@@ -158,10 +158,9 @@ struct APIRouter
         slim = !env.params.query["slim"]?.nil?
         shallow = !env.params.query["shallow"]?.nil?
 
-        json = JSON.build do |j|
-          title.build_json j, slim: slim, shallow: shallow,
-            sort_context: {username: username, opt: sort_opt}
-        end
+        send_json env, title.build_json(slim: slim, shallow: shallow,
+          sort_context: {username: username,
+                         opt:      sort_opt})
       rescue e
         Logger.error e
         env.response.status_code = 404
@@ -184,10 +183,7 @@ struct APIRouter
       slim = !env.params.query["slim"]?.nil?
       shallow = !env.params.query["shallow"]?.nil?
 
-      json = JSON.build do |j|
-        Library.default.build_json j, slim: slim, shallow: shallow
-      end
-      send_json env, json
+      send_json env, Library.default.build_json(slim: slim, shallow: shallow)
     end
 
     Koa.describe "Triggers a library scan"