diff --git a/bindings/python/cconfigspace/expression.py b/bindings/python/cconfigspace/expression.py
index 24bee6dc01ae429f53a9fa1145d7192a6740c8f4..b88c698ff9d5b2d72e4beebea8d706e25af175f9 100644
--- a/bindings/python/cconfigspace/expression.py
+++ b/bindings/python/cconfigspace/expression.py
@@ -216,6 +216,12 @@ class Literal(Expression):
     v = self.value
     if isinstance(v, str):
       return repr(v)
+    elif v is None:
+      return "none"
+    elif v is True:
+      return "true"
+    elif v is False:
+      return "false"
     else:
       return "{}".format(v)
 
diff --git a/bindings/python/cconfigspace/expression_parser.py b/bindings/python/cconfigspace/expression_parser.py
index f61624359a75f846fd5f941b91d077937aad545b..1a2fc28bc4d6261a3d25214ba686bc1fe8722e07 100644
--- a/bindings/python/cconfigspace/expression_parser.py
+++ b/bindings/python/cconfigspace/expression_parser.py
@@ -21,15 +21,17 @@ list: '[' list_item ']'
 list_item: list_item ',' value
          | value;
 value: none
-     | boolean
+     | btrue
+     | bfalse
      | string
      | identifier
      | integer
      | float;
 
 terminals
-none: /None/ {prefer};
-boolean: /True|False/ {prefer};
+none: /none/ {prefer};
+btrue: /true/ {prefer};
+bfalse: /false/ {prefer};
 identifier: /[a-zA-Z_][a-zA-Z_0-9]*/;
 string: /"([^\0\t\n\r\f"\\]|\\[0tnrf"\\])+"|'([^\0\t\n\r\f'\\]|\\[0tnrf'\\])+'/;
 integer: /-?[0-9]+/;
@@ -53,8 +55,9 @@ _actions["list_item"] = [
   lambda _, n: n[0] + [n[2]],
   lambda _, n: [n[0]]
 ]
-_actions["none"] = lambda _, value: Literal(value = eval(value))
-_actions["boolean"] = lambda _, value: Literal(value = eval(value))
+_actions["none"] = lambda _, value: Literal(value = None)
+_actions["btrue"] = lambda _, value: Literal(value = True)
+_actions["bfalse"] = lambda _, value: Literal(value = False)
 _actions["identifier"] = lambda p, value: Variable(hyperparameter = p.extra.hyperparameter_by_name(value))
 _actions["string"] = lambda _, value: Literal(value = eval(value))
 _actions["float"] = lambda _, value: Literal(value = float(value))
diff --git a/bindings/python/test/test_expression.py b/bindings/python/test/test_expression.py
index 86670dbbe3224419c3899c8fd9ca8e6853ae34c1..923f59f5f0e5f2dd0b4da89b6afec2ccf14f4103 100644
--- a/bindings/python/test/test_expression.py
+++ b/bindings/python/test/test_expression.py
@@ -32,7 +32,7 @@ class TestExpression(unittest.TestCase):
     e = ccs.Literal(value = 15)
     self.assertEqual( "15" , str(e) )
     e = ccs.Literal(value = None)
-    self.assertEqual( "None" , str(e) )
+    self.assertEqual( "none" , str(e) )
 
   def test_variable(self):
     h = ccs.NumericalHyperparameter()
@@ -51,12 +51,12 @@ class TestExpression(unittest.TestCase):
 
   def test_unary(self):
     e = ccs.Expression.unary(t = ccs.NOT, node = True)
-    self.assertEqual( "!True", str(e) )
+    self.assertEqual( "!true", str(e) )
     self.assertFalse( e.eval() )
 
   def test_binary(self):
     e = ccs.Expression.binary(t = ccs.OR, left = True, right = False)
-    self.assertEqual( "True || False", str(e) )
+    self.assertEqual( "true || false", str(e) )
     self.assertTrue( e.eval() )
 
 if __name__ == '__main__':
diff --git a/bindings/python/test/test_expression_parser.py b/bindings/python/test/test_expression_parser.py
index 475a1c44c6f644c27e60d1947e04f3b3337d9aa1..1952c9dbd12e9d9846a7b47d98d9e35f3379fde7 100644
--- a/bindings/python/test/test_expression_parser.py
+++ b/bindings/python/test/test_expression_parser.py
@@ -39,23 +39,23 @@ class TestExpressionParser(unittest.TestCase):
     self.assertFalse( res.eval() )
 
   def test_boolean(self):
-    exp = "True"
+    exp = "true"
     res = ccs.ccs_parser.parse(exp)
     self.assertIsInstance( res, ccs.Literal )
     self.assertEqual( True, res.eval() )
-    self.assertEqual( "True", res.__str__() )
-    exp = "False"
+    self.assertEqual( "true", res.__str__() )
+    exp = "false"
     res = ccs.ccs_parser.parse(exp)
     self.assertIsInstance( res, ccs.Literal )
     self.assertEqual( False, res.eval() )
-    self.assertEqual( "False", res.__str__() )
+    self.assertEqual( "false", res.__str__() )
 
   def test_none(self):
-    exp = "None"
+    exp = "none"
     res = ccs.ccs_parser.parse(exp)
     self.assertIsInstance( res, ccs.Literal )
     self.assertIsNone( res.eval() )
-    self.assertEqual( "None", res.__str__() )
+    self.assertEqual( "none", res.__str__() )
 
 
 if __name__ == '__main__':
diff --git a/bindings/ruby/lib/cconfigspace/expression.rb b/bindings/ruby/lib/cconfigspace/expression.rb
index fa6cc1bebe53dcb0061f8cb9a1ba03e4c4c33452..3e797dceca440413d6da81f1beca48e6ef71102c 100644
--- a/bindings/ruby/lib/cconfigspace/expression.rb
+++ b/bindings/ruby/lib/cconfigspace/expression.rb
@@ -206,7 +206,9 @@ module CCS
 
     def to_s
       case value
-      when nil, String
+      when nil
+        "none"
+      when String
         value.inspect
       else
         value.to_s
diff --git a/bindings/ruby/lib/cconfigspace/expression_parser.rb b/bindings/ruby/lib/cconfigspace/expression_parser.rb
index 53b4fb6b2709ddbc4637005174e86e0271404517..6452f7352e7af4446cd7d2fb9880b8b725353e2e 100644
--- a/bindings/ruby/lib/cconfigspace/expression_parser.rb
+++ b/bindings/ruby/lib/cconfigspace/expression_parser.rb
@@ -43,10 +43,12 @@ module CCS
     rule("]")
     rule(",")
 
-    rule(:none => /nil/).as { |b|
+    rule(:none => /none/).as { |b|
       Literal::new(value: nil) }
-    rule(:boolean => /true|false/).as { |b|
-      Literal::new(value: eval(b)) }
+    rule(:btrue => /true/).as { |b|
+      Literal::new(value: true) }
+    rule(:bfalse => /false/).as { |b|
+      Literal::new(value: false) }
     rule(:float => /-?[0-9]+([eE][+-]?[0-9]+|\.[0-9]+([eE][+-]?[0-9]+)?)/).as {|num|
       Literal::new(value: Float(num)) }
     rule(:integer => /-?[0-9]+/).as { |num|
@@ -58,7 +60,8 @@ module CCS
 
     rule(:value) do |r|
       r[:none]
-      r[:boolean]
+      r[:btrue]
+      r[:bfalse]
       r[:string]
       r[:identifier]
       r[:float]
diff --git a/bindings/ruby/test/test_expression_parser.rb b/bindings/ruby/test/test_expression_parser.rb
index 5185837b957a7585f4a7e4c2909bcc5caf37146c..7f134e11dae5ab98906948bd41247b74538ab8c2 100644
--- a/bindings/ruby/test/test_expression_parser.rb
+++ b/bindings/ruby/test/test_expression_parser.rb
@@ -63,11 +63,11 @@ class CConfigSpaceTestExpressionParser < Minitest::Test
 
   def test_none
     m = CCS::ExpressionParser.new.method(:parse)
-    exp = "nil"
+    exp = "none"
     res = m[exp]
     assert( res.kind_of? CCS::Literal )
     assert_nil( res.eval )
-    assert_equal( "nil", res.to_s )
+    assert_equal( "none", res.to_s )
   end
 
 end