diff --git a/lib/ttfunk/subset_collection.rb b/lib/ttfunk/subset_collection.rb
index bb72702f..d63d5f3e 100644
--- a/lib/ttfunk/subset_collection.rb
+++ b/lib/ttfunk/subset_collection.rb
@@ -38,6 +38,8 @@ def use(characters)
     # and so may not look (in the raw) like what was passed in, but
     # they will render correctly with the indicated subset font.
     def encode(characters)
+      return [] if characters.empty?
+
       # TODO: probably would be more optimal to nix the #use method,
       # and merge it into this one, so it can be done in a single
       # pass instead of two passes.