diff --git a/lib/fugit/duration.rb b/lib/fugit/duration.rb
index d972266..bdc3420 100644
--- a/lib/fugit/duration.rb
+++ b/lib/fugit/duration.rb
@@ -68,8 +68,10 @@ def common_rewrite_dur(t)
       hou: { a: 'h', r: 'h', i: 'H', s: 3600, I: true, l: 'hour' },
       min: { a: 'm', r: 'm', i: 'M', s: 60, I: true, l: 'minute' },
       sec: { a: 's', r: 's', i: 'S', s: 1, I: true, l: 'second' } }.freeze
-    INFLA_KEYS, NON_INFLA_KEYS =
-      KEYS.partition { |k, v| v[:I] }.freeze
+
+    INFLA_KEYS, NON_INFLA_KEYS = KEYS
+      .partition { |k, v| v[:I] }
+      .collect(&:freeze)
 
     def _to_s(key)