diff --git a/extra_test.go b/extra_test.go
index a794211..89482a3 100644
--- a/extra_test.go
+++ b/extra_test.go
@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	. "github.com/yuin/goldmark"
+	"github.com/yuin/goldmark/parser"
 	"github.com/yuin/goldmark/renderer/html"
 	"github.com/yuin/goldmark/testutil"
 )
@@ -57,3 +58,29 @@ func TestWindowsNewLine(t *testing.T) {
 		t.Errorf("\n%s\n---------\n%s", source, b2.String())
 	}
 }
+
+type myIDs struct {
+}
+
+func (s *myIDs) Generate(value, prefix []byte) []byte {
+	return []byte("my-id")
+}
+
+func (s *myIDs) Put(value []byte) {
+}
+
+func TestAutogeneratedIDs(t *testing.T) {
+	ctx := parser.NewContext(parser.WithIDs(&myIDs{}))
+	markdown := New(WithParserOptions(parser.WithAutoHeadingID()))
+	source := []byte("# Title1\n## Title2")
+	var b bytes.Buffer
+	err := markdown.Convert(source, &b, parser.WithContext(ctx))
+	if err != nil {
+		t.Error(err.Error())
+	}
+	if b.String() != `<h1 id="my-id">Title1</h1>
+<h2 id="my-id">Title2</h2>
+` {
+		t.Errorf("%s\n---------\n%s", source, b.String())
+	}
+}
diff --git a/parser/parser.go b/parser/parser.go
index 1d9487a..b536fd5 100644
--- a/parser/parser.go
+++ b/parser/parser.go
@@ -88,7 +88,7 @@ func (s *ids) Generate(value, prefix []byte) []byte {
 				v += 'a' - 'A'
 			}
 			result = append(result, v)
-		} else if util.IsSpace(v) {
+		} else if util.IsSpace(v) || v == '-' || v == '_' {
 			result = append(result, '-')
 		}
 	}
@@ -104,7 +104,7 @@ func (s *ids) Generate(value, prefix []byte) []byte {
 		return result
 	}
 	for i := 1; ; i++ {
-		newResult := fmt.Sprintf("%s%d", result, i)
+		newResult := fmt.Sprintf("%s-%d", result, i)
 		if _, ok := s.values[newResult]; !ok {
 			s.values[newResult] = true
 			return []byte(newResult)
@@ -198,6 +198,20 @@ type Context interface {
 	LastOpenedBlock() Block
 }
 
+// A ContextConfig struct is a data structure that holds configuration of the Context.
+type ContextConfig struct {
+	IDs IDs
+}
+
+// An ContextOption is a functional option type for the Context.
+type ContextOption func(*ContextConfig)
+
+func WithIDs(ids IDs) ContextOption {
+	return func(c *ContextConfig) {
+		c.IDs = ids
+	}
+}
+
 type parseContext struct {
 	store         []interface{}
 	ids           IDs
@@ -210,11 +224,18 @@ type parseContext struct {
 }
 
 // NewContext returns a new Context.
-func NewContext() Context {
+func NewContext(options ...ContextOption) Context {
+	cfg := &ContextConfig{
+		IDs: newIDs(),
+	}
+	for _, option := range options {
+		option(cfg)
+	}
+
 	return &parseContext{
 		store:         make([]interface{}, ContextKeyMax+1),
 		refs:          map[string]Reference{},
-		ids:           newIDs(),
+		ids:           cfg.IDs,
 		blockOffset:   -1,
 		blockIndent:   -1,
 		delimiters:    nil,