diff --git a/lib/typed/tree/basic_values.rb b/lib/typed/tree/basic_values.rb
index 3b744423..fc2b6bd8 100644
--- a/lib/typed/tree/basic_values.rb
+++ b/lib/typed/tree/basic_values.rb
@@ -21,7 +21,7 @@ module Typed
     end
     class FalseExpression < Expression
       def to_s
-        false
+        "false"
       end
     end
     class NilExpression < Expression
diff --git a/test/typed/expressions/helper.rb b/test/typed/expressions/helper.rb
index fcb12cee..21a48430 100644
--- a/test/typed/expressions/helper.rb
+++ b/test/typed/expressions/helper.rb
@@ -6,6 +6,7 @@ module ExpressionHelper
     Register.machine.boot unless Register.machine.booted
     compiler = Typed::MethodCompiler.new Register.machine.space.get_main
     code = Typed.ast_to_code @input
+    assert code.to_s , @input
     produced = compiler.process( code )
     assert @output , "No output given"
     assert_equal produced.class , @output , "Wrong class"
diff --git a/test/typed/statements/helper.rb b/test/typed/statements/helper.rb
index 4236cd60..cf490fbf 100644
--- a/test/typed/statements/helper.rb
+++ b/test/typed/statements/helper.rb
@@ -13,7 +13,9 @@ module Statements
   def check
     assert @expect , "No output given"
     compiler = Typed::MethodCompiler.new
-    produced = compiler.process( Typed.ast_to_code( @input) )
+    code = Typed.ast_to_code( @input )
+    assert code.to_s , @input
+    produced = compiler.process( code )
     produced = Register.machine.space.get_main.instructions
     compare_instructions produced , @expect
     produced