diff --git a/cmd/postgresql-upgrade-database.rb b/cmd/postgresql-upgrade-database.rb
index 36bc67aee07..f4c1d790b2d 100755
--- a/cmd/postgresql-upgrade-database.rb
+++ b/cmd/postgresql-upgrade-database.rb
@@ -104,7 +104,7 @@ module Homebrew
         initdb_args += if setting == "server_encoding"
           ["-E #{value}"]
         else
-          ["--#{setting.tr!("_", "-")}=#{value}"]
+          ["--#{setting.tr("_", "-")}=#{value}"]
         end
       end