diff --git a/app/models/derived_variables/lettings_log_variables.rb b/app/models/derived_variables/lettings_log_variables.rb
index ac17e0219..11d03bdcb 100644
--- a/app/models/derived_variables/lettings_log_variables.rb
+++ b/app/models/derived_variables/lettings_log_variables.rb
@@ -116,6 +116,7 @@ module DerivedVariables::LettingsLogVariables
     if uprn_confirmed&.zero?
       self.uprn = nil
       self.uprn_known = 0
+      self.uprn_confirmed = nil
     end
 
     self.nationality_all = nationality_all_group if nationality_uk_or_prefers_not_to_say?
diff --git a/app/models/derived_variables/sales_log_variables.rb b/app/models/derived_variables/sales_log_variables.rb
index a4817a230..2e9d5434a 100644
--- a/app/models/derived_variables/sales_log_variables.rb
+++ b/app/models/derived_variables/sales_log_variables.rb
@@ -47,6 +47,7 @@ module DerivedVariables::SalesLogVariables
     if uprn_confirmed&.zero?
       self.uprn = nil
       self.uprn_known = 0
+      self.uprn_confirmed = nil
     end
 
     self.nationality_all = nationality_all_group if nationality_uk_or_prefers_not_to_say?
diff --git a/spec/shared/shared_examples_for_derived_fields.rb b/spec/shared/shared_examples_for_derived_fields.rb
index 6382ef4f4..336cbf852 100644
--- a/spec/shared/shared_examples_for_derived_fields.rb
+++ b/spec/shared/shared_examples_for_derived_fields.rb
@@ -14,4 +14,14 @@ RSpec.shared_examples "shared examples for derived fields" do |log_type|
       expect { log.set_derived_fields! }.not_to change(log, :ethnic)
     end
   end
+
+  context "when uprn is not confirmed" do
+    it "derives other uprn fields correctly" do
+      log = FactoryBot.build(log_type, uprn_known: 1, uprn: 1, uprn_confirmed: 0)
+
+      expect { log.set_derived_fields! }.to change(log, :uprn_known).from(1).to(0)
+      .and change(log, :uprn).from("1").to(nil)
+      .and change(log, :uprn_confirmed).from(0).to(nil)
+    end
+  end
 end