diff --git a/src/library.cr b/src/library.cr
index a582089a..73e0f130 100644
--- a/src/library.cr
+++ b/src/library.cr
@@ -536,6 +536,8 @@ class Library
 
   def initialize
     @storage = Storage.default
+    register_mime_types
+
     @dir = Config.current.library_path
     @scan_interval = Config.current.scan_interval
     # explicitly initialize @titles to bypass the compiler check. it will
diff --git a/src/util.cr b/src/util.cr
index 57d0e9bf..74678896 100644
--- a/src/util.cr
+++ b/src/util.cr
@@ -41,8 +41,6 @@ def send_json(env, json)
 end
 
 def send_attachment(env, path)
-  MIME.register ".cbz", "application/vnd.comicbook+zip"
-  MIME.register ".cbr", "application/vnd.comicbook-rar"
   send_file env, path, filename: File.basename(path), disposition: "attachment"
 end
 
@@ -164,3 +162,14 @@ def escape_xml(str)
     '&'  => "&",
   })
 end
+
+def register_mime_types
+  {
+    ".zip" => "application/zip",
+    ".rar" => "application/x-rar-compressed",
+    ".cbz" => "application/vnd.comicbook+zip",
+    ".cbr" => "application/vnd.comicbook-rar",
+  }.each do |k, v|
+    MIME.register k, v
+  end
+end