diff --git a/modplug-tools.rb b/modplug-tools.rb
index cbe43b9..81b0e22 100644
--- a/modplug-tools.rb
+++ b/modplug-tools.rb
@@ -7,6 +7,7 @@ class ModplugTools < Formula
 
   depends_on "cmake" => :build
   depends_on "libmodplug"
+  depends_on "libao"
 
   def install
     system "cmake", "."