diff --git a/app/models/log.rb b/app/models/log.rb
index bcbea9c92..4471e38eb 100644
--- a/app/models/log.rb
+++ b/app/models/log.rb
@@ -110,7 +110,7 @@ class Log < ApplicationRecord
         self.address_line2 = nil
         self.town_or_city = nil
         self.county = nil
-        self.postcode_full = postcode_full_input
+        self.postcode_full = postcode_full_input if postcode_full_input.match(POSTCODE_REGEXP)
         process_postcode_changes!
       else
         self.uprn = uprn_selection
diff --git a/spec/features/lettings_log_spec.rb b/spec/features/lettings_log_spec.rb
index b10dfc6e5..525dee9ff 100644
--- a/spec/features/lettings_log_spec.rb
+++ b/spec/features/lettings_log_spec.rb
@@ -1018,6 +1018,33 @@ RSpec.describe "Lettings Log Features" do
           end
         end
 
+        context "and the user selects 'address_not_listed' when partial postcode is entered" do
+          before do
+            fill_in("lettings_log[address_line1_input]", with: "Address line 1")
+            fill_in("lettings_log[postcode_full_input]", with: "AA1")
+            click_button("Search")
+            choose "The address is not listed, I want to enter the address manually"
+            click_button("Save and continue")
+          end
+
+          it "sets correct address fields" do
+            lettings_log.reload
+            expect(lettings_log.uprn_known).to eq(0) # no
+            expect(lettings_log.uprn).to eq(nil)
+            expect(lettings_log.uprn_confirmed).to eq(nil)
+            expect(lettings_log.uprn_selection).to eq("uprn_not_listed")
+            expect(lettings_log.postcode_known).to eq(nil)
+            expect(lettings_log.postcode_full).to eq(nil)
+            expect(lettings_log.address_line1).to eq("Address line 1")
+            expect(lettings_log.address_line2).to eq(nil)
+            expect(lettings_log.town_or_city).to eq(nil)
+            expect(lettings_log.address_line1_input).to eq("Address line 1")
+            expect(lettings_log.postcode_full_input).to eq("AA1")
+            expect(lettings_log.address_search_value_check).to eq(nil)
+            expect(lettings_log.la).to eq(nil)
+          end
+        end
+
         context "and the user selects 'address_not_listed' and then changes their mind and selects an address" do
           before do
             fill_in("lettings_log[address_line1_input]", with: "Address line 1")
diff --git a/spec/features/sales_log_spec.rb b/spec/features/sales_log_spec.rb
index d418bcb37..663a4f7ac 100644
--- a/spec/features/sales_log_spec.rb
+++ b/spec/features/sales_log_spec.rb
@@ -599,6 +599,33 @@ RSpec.describe "Sales Log Features" do
           end
         end
 
+        context "and the user selects 'address_not_listed' when partial postcode is given" do
+          before do
+            fill_in("sales_log[address_line1_input]", with: "Address line 1")
+            fill_in("sales_log[postcode_full_input]", with: "1AA")
+            click_button("Search")
+            choose "The address is not listed, I want to enter the address manually"
+            click_button("Save and continue")
+          end
+
+          it "sets correct address fields" do
+            sales_log.reload
+            expect(sales_log.uprn_known).to eq(0) # no
+            expect(sales_log.uprn).to eq(nil)
+            expect(sales_log.uprn_confirmed).to eq(nil)
+            expect(sales_log.uprn_selection).to eq("uprn_not_listed")
+            expect(sales_log.pcodenk).to eq(nil)
+            expect(sales_log.postcode_full).to eq(nil)
+            expect(sales_log.address_line1).to eq("Address line 1")
+            expect(sales_log.address_line2).to eq(nil)
+            expect(sales_log.town_or_city).to eq(nil)
+            expect(sales_log.address_line1_input).to eq("Address line 1")
+            expect(sales_log.postcode_full_input).to eq("1AA")
+            expect(sales_log.address_search_value_check).to eq(nil)
+            expect(sales_log.la).to eq(nil)
+          end
+        end
+
         context "and the user selects 'address_not_listed' and then changes their mind and selects an address" do
           before do
             fill_in("sales_log[address_line1_input]", with: "Address line 1")