diff --git a/lib/puppet/pops/types/types.rb b/lib/puppet/pops/types/types.rb
index <HASH>..<HASH> 100644
--- a/lib/puppet/pops/types/types.rb
+++ b/lib/puppet/pops/types/types.rb
@@ -550,7 +550,7 @@ class PUndefType < PAnyType
   end
 
   def instance?(o, guard = nil)
-    o.nil? || o == :undef
+    o.nil? || :undef == o
   end
 
   # @api private
(maint) Work around for semantic-puppet bug PUP-<I>

Comparing versions with non-versions requires that the non-version is on
the LHS of the expression.