3 files changed, 10 insertions, 2 deletions
diff --git a/ast.c b/ast.c
index c3f28eba0b..2df4bdd870 100644
--- a/ast.c
+++ b/ast.c
@@ -96,7 +96,7 @@ rb_ast_parse_str(VALUE str)
 {
     rb_ast_t *ast = 0;
 
-    str = rb_check_string_type(str);
+    StringValue(str);
     ast = rb_parser_compile_string_path(ast_parse_new(), Qnil, str, 1);
     return ast_parse_done(ast);
 }
diff --git a/test/ruby/test_ast.rb b/test/ruby/test_ast.rb
index 055567d574..23cd5618a0 100644
--- a/test/ruby/test_ast.rb
+++ b/test/ruby/test_ast.rb
@@ -134,6 +134,14 @@ class TestAst < Test::Unit::TestCase
     assert_raise(TypeError) {RubyVM::AbstractSyntaxTree::Node.allocate}
   end
 
+  def test_parse_argument_error
+    assert_raise(TypeError) {RubyVM::AbstractSyntaxTree.parse(0)}
+    assert_raise(TypeError) {RubyVM::AbstractSyntaxTree.parse(nil)}
+    assert_raise(TypeError) {RubyVM::AbstractSyntaxTree.parse(false)}
+    assert_raise(TypeError) {RubyVM::AbstractSyntaxTree.parse(true)}
+    assert_raise(TypeError) {RubyVM::AbstractSyntaxTree.parse(:foo)}
+  end
+
   def test_column_with_long_heredoc_identifier
     term = "A"*257
     ast = RubyVM::AbstractSyntaxTree.parse("<<-#{term}\n""ddddddd\n#{term}\n")
diff --git a/version.h b/version.h
index 8651698333..519289ce60 100644
--- a/version.h
+++ b/version.h
@@ -1,6 +1,6 @@
 #define RUBY_VERSION "2.6.0"
 #define RUBY_RELEASE_DATE RUBY_RELEASE_YEAR_STR"-"RUBY_RELEASE_MONTH_STR"-"RUBY_RELEASE_DAY_STR
-#define RUBY_PATCHLEVEL 11
+#define RUBY_PATCHLEVEL 12
 
 #define RUBY_RELEASE_YEAR 2019
 #define RUBY_RELEASE_MONTH 1