diff --git a/app/controllers/imports_controller.rb b/app/controllers/imports_controller.rb
index 9431ca098..a5248dc1e 100644
--- a/app/controllers/imports_controller.rb
+++ b/app/controllers/imports_controller.rb
@@ -173,7 +173,7 @@ class ImportsController < ApplicationController
     return if @import.settings['encoding'].blank?
 
     mappings = @import.settings['mapping'] ||= {}
-    headers = @import.headers.map(&:downcase)
+    headers = @import.headers.map{|header| header.to_s.downcase}
 
     # Core fields
     import_type::AUTO_MAPPABLE_FIELDS.each do |field_nm, label_nm|
diff --git a/test/fixtures/files/import_issues_auto_mapping.csv b/test/fixtures/files/import_issues_auto_mapping.csv
index 49785f7a4..61f3e8357 100644
--- a/test/fixtures/files/import_issues_auto_mapping.csv
+++ b/test/fixtures/files/import_issues_auto_mapping.csv
@@ -1,2 +1,2 @@
-priority;Subject;start_date;parent;private;progress;custom;"target version";category;user;estimated_hours;tracker;status;database;cf_6
-High;First;2015-07-08;;no;;PostgreSQL;;New category;dlopper;1;bug;new;"PostgreSQL, Oracle";2
+priority;;Subject;start_date;parent;private;progress;custom;"target version";category;user;estimated_hours;tracker;status;database;cf_6
+High;;First;2015-07-08;;no;;PostgreSQL;;New category;dlopper;1;bug;new;"PostgreSQL, Oracle";2
diff --git a/test/functional/imports_controller_test.rb b/test/functional/imports_controller_test.rb
index 8a69c7dee..fc833ec4a 100644
--- a/test/functional/imports_controller_test.rb
+++ b/test/functional/imports_controller_test.rb
@@ -190,19 +190,19 @@ class ImportsControllerTest < Redmine::ControllerTest
     #  - 'Subject' exists in the import file
     #  - mapping is case insensitive
     assert_select 'select[name=?]', 'import_settings[mapping][subject]' do
-      assert_select 'option[value="1"][selected="selected"]', :text => 'Subject'
+      assert_select 'option[value="2"][selected="selected"]', :text => 'Subject'
     end
 
     # 'estimated_hours' should be auto selected because
     #  - 'estimated_hours' exists in the import file
     assert_select 'select[name=?]', 'import_settings[mapping][estimated_hours]' do
-      assert_select 'option[value="10"][selected="selected"]', :text => 'estimated_hours'
+      assert_select 'option[value="11"][selected="selected"]', :text => 'estimated_hours'
     end
 
     # 'fixed_version' should be auto selected because
     #  - the translation 'Target version' exists in the import file
     assert_select 'select[name=?]', 'import_settings[mapping][fixed_version]' do
-      assert_select 'option[value="7"][selected="selected"]', :text => 'target version'
+      assert_select 'option[value="8"][selected="selected"]', :text => 'target version'
     end
 
     # 'assigned_to' should not be auto selected because
@@ -214,14 +214,14 @@ class ImportsControllerTest < Redmine::ControllerTest
     # Custom field 'Float field' should be auto selected because
     #  - the internal field name ('cf_6') exists in the import file
     assert_select 'select[name=?]', 'import_settings[mapping][cf_6]' do
-      assert_select 'option[value="14"][selected="selected"]', :text => 'cf_6'
+      assert_select 'option[value="15"][selected="selected"]', :text => 'cf_6'
     end
 
     # Custom field 'Database' should be auto selected because
     #  - field name 'database' exists in the import file
     #  - mapping is case insensitive
     assert_select 'select[name=?]', 'import_settings[mapping][cf_1]' do
-      assert_select 'option[value="13"][selected="selected"]', :text => 'database'
+      assert_select 'option[value="14"][selected="selected"]', :text => 'database'
     end
   end