diff --git a/Library/Homebrew/build.rb b/Library/Homebrew/build.rb
index c4e903642b..c0f15158d1 100644
--- a/Library/Homebrew/build.rb
+++ b/Library/Homebrew/build.rb
@@ -48,7 +48,7 @@ class Build
         Requirement.prune
       elsif req.build? && dependent != formula
         Requirement.prune
-      elsif req.satisfied? && req.default_formula? && (dep = req.to_dependency).installed?
+      elsif req.satisfied? && (dep = req.to_dependency) && dep.installed?
         deps << dep
         Requirement.prune
       end