diff --git a/lib/sproutcore/models/manifest.rb b/lib/sproutcore/models/manifest.rb
index 8440fcc..f4d70f6 100644
--- a/lib/sproutcore/models/manifest.rb
+++ b/lib/sproutcore/models/manifest.rb
@@ -277,7 +277,10 @@ def entry_for(filename, opts = {})
         manifest = self
         filename = target_name
       else
-        manifest = target.target_for(target_name).manifest_for(self.variation)
+        if (_manifest_target = target.target_for(target_name)).nil?
+          throw "Cannot file target #{target_name} for entry #{filename}"
+        end
+        manifest = _manifest_target.manifest_for(self.variation)
         manifest.build!
       end