diff --git a/lib/rspayd/czech_payment.rb b/lib/rspayd/czech_payment.rb
index 96c5d66..c23ac74 100644
--- a/lib/rspayd/czech_payment.rb
+++ b/lib/rspayd/czech_payment.rb
@@ -10,7 +10,7 @@ class CzechPayment < Payment
     # vs            - Variabilní symbol.
     # ss            - Specifický symbol.
 
-    attr_reader :accountPrefix, :accountNumber, :bankCode, :vs, :ss
+    attr_reader :accountPrefix, :accountNumber, :bankCode, :vs, :ss, :ks
 
     def initialize(options)
       options = Hash[options.map { |(k, v)| [k.to_sym, v] }]
@@ -29,6 +29,7 @@ def initialize(options)
 
       @vs = options[:vs]
       @ss = options[:ss]
+      @ks = options[:ks]
 
       super
     end
@@ -46,6 +47,7 @@ def to_s
       out = [ super ]
       out << "*X-VS:#{vs}" if vs
       out << "*X-SS:#{ss}" if ss
+      out << "*X-KS:#{ks}" if ks
       out.join
     end
   end
diff --git a/test/czech_payment_test.rb b/test/czech_payment_test.rb
index 52d73ff..86362c7 100644
--- a/test/czech_payment_test.rb
+++ b/test/czech_payment_test.rb
@@ -60,6 +60,20 @@ def test_sample_payment
     assert_equal 'SPD*1.0*ACC:CZ5855000000001265098001*AM:480.50*CC:CZK*RF:7004139146*DT:20120524*MSG:PLATBA ZA ZBOZI*X-SS:1234567890', result
   end
 
+  def test_czech_payment_with_constant_symbol
+    result = Rspayd::CzechPayment.generate_string(
+      :accountNumber => '810883001',
+      :bankCode => '5500',
+      :amount => 430.00,
+      :vs => '31030001',
+      :ks => '1234567890',
+      :message => 'Platba za domenu'
+    )
+
+    assert_equal 'SPD*1.0*ACC:CZ9555000000000810883001*AM:430.00*CC:CZK*MSG:PLATBA ZA DOMENU*X-VS:31030001*X-KS:1234567890', result
+  end
+
+
   def test_iban_checksum_prepend
     result = Rspayd::CzechPayment.new(
       :accountNumber => '2950281886',