diff --git a/lib/registration.rb b/lib/registration.rb
index 4ee8a8a16ac6c52762252311f0fe10bbcf12e1f4..236bd196670b4ba716513298bcd3532aac051573 100644
--- a/lib/registration.rb
+++ b/lib/registration.rb
@@ -353,12 +353,14 @@ class Registration
 
 			def write
 				Command.reply { |reply|
-					reply.allowed_actions = [:next]
+					reply.allowed_actions = [:next, :prev]
 					add_form(reply)
 				}.then(&method(:parse))
 			end
 
 			def parse(iq)
+				return Activation.for(@customer, @tel).then(&:write) if iq.prev?
+
 				guard_too_many_tries.then {
 					verify(iq.form.field("code")&.value&.to_s)
 				}.then {