diff --git a/app/models/search_log.rb b/app/models/search_log.rb
index 80068d3414b..c74d97bb0fb 100644
--- a/app/models/search_log.rb
+++ b/app/models/search_log.rb
@@ -41,6 +41,7 @@ class SearchLog < ActiveRecord::Base
     search_type = search_types[search_type]
     return [:error] unless search_type.present? && ip_address.present?
 
+    ip_address = nil if user_id
     key = redis_key(user_id: user_id, ip_address: ip_address)
 
     result = nil
@@ -143,7 +144,7 @@ end
 #  id                 :integer          not null, primary key
 #  term               :string           not null
 #  user_id            :integer
-#  ip_address         :inet             not null
+#  ip_address         :inet
 #  search_result_id   :integer
 #  search_type        :integer          not null
 #  created_at         :datetime         not null
diff --git a/db/migrate/20180521184439_allow_null_ip_search_log.rb b/db/migrate/20180521184439_allow_null_ip_search_log.rb
new file mode 100644
index 00000000000..19566c4d9f2
--- /dev/null
+++ b/db/migrate/20180521184439_allow_null_ip_search_log.rb
@@ -0,0 +1,13 @@
+class AllowNullIpSearchLog < ActiveRecord::Migration[5.1]
+  def up
+    begin
+      Migration::SafeMigrate.disable!
+      change_column :search_logs, :ip_address, :inet, null: true
+    ensure
+      Migration::SafeMigrate.enable!
+    end
+  end
+
+  def down
+  end
+end