diff --git a/lib/omnibus/builder.rb b/lib/omnibus/builder.rb
index 5370724e3..c64272fd2 100644
--- a/lib/omnibus/builder.rb
+++ b/lib/omnibus/builder.rb
@@ -217,7 +217,7 @@ def configure(*args)
 
       # Accept a prefix override if provided. Can be set to '' to suppress
       # this functionality.
-      default_prefix = unless windows? then "#{install_dir}/embedded" else python_3_embedded end
+      default_prefix = if !windows? then "#{install_dir}/embedded" else python_3_embedded end
       prefix = options.delete(:prefix) || default_prefix
       configure_cmd << "--prefix=#{prefix}" if prefix && prefix != ""