diff --git a/lib/heroku/command/pg_backups.rb b/lib/heroku/command/pg_backups.rb
index <HASH>..<HASH> 100644
--- a/lib/heroku/command/pg_backups.rb
+++ b/lib/heroku/command/pg_backups.rb
@@ -112,13 +112,13 @@ class Heroku::Command::Pg < Heroku::Command::Base
   end
 
   def size_pretty(bytes)
-    suffixes = {
-      'B'  => 1,
-      'kB' => 1_000,
-      'MB' => 1_000_000,
-      'GB' => 1_000_000_000,
-      'TB' => 1_000_000_000_000 # (ohdear)
-    }
+    suffixes = [
+      ['B', 1],
+      ['kB', 1_000],
+      ['MB', 1_000_000],
+      ['GB', 1_000_000_000],
+      ['TB', 1_000_000_000_000] # (ohdear)
+    ]
     suffix, multiplier = suffixes.find do |k,v|
       normalized = bytes / v.to_f
       normalized >= 0 && normalized < 1_000
Fix size_pretty on <I> since it doesn't guarantee hash key order