diff --git a/parser/src/parser.rs b/parser/src/parser.rs
index 6aae44d..9bdf9a6 100644
--- a/parser/src/parser.rs
+++ b/parser/src/parser.rs
@@ -49,8 +49,14 @@ pub enum Event {
     StreamStart,
     /// Last event that will be generated by the parser. Signals EOF.
     StreamEnd,
-    /// The YAML start document directive (`---`).
-    DocumentStart,
+    /// The start of a YAML document.
+    ///
+    /// When the boolean is `true`, it is an explicit document start
+    /// directive (`---`).
+    ///
+    /// When the boolean is `false`, it is an implicit document start
+    /// (without `---`).
+    DocumentStart(bool),
     /// The YAML end document directive (`...`).
     DocumentEnd,
     /// A YAML Alias.
@@ -441,7 +447,7 @@ impl<T: Input> Parser<T> {
         span: Span,
         recv: &mut R,
     ) -> Result<(), ScanError> {
-        if first_ev != Event::DocumentStart {
+        if !matches!(first_ev, Event::DocumentStart(_)) {
             return Err(ScanError::new_str(
                 span.start,
                 "did not find expected <document-start>",
@@ -599,7 +605,7 @@ impl<T: Input> Parser<T> {
                 self.parser_process_directives()?;
                 self.push_state(State::DocumentEnd);
                 self.state = State::BlockNode;
-                Ok((Event::DocumentStart, span))
+                Ok((Event::DocumentStart(false), span))
             }
             _ => {
                 // explicit document
@@ -648,7 +654,7 @@ impl<T: Input> Parser<T> {
                 self.push_state(State::DocumentEnd);
                 self.state = State::DocumentContent;
                 self.skip();
-                Ok((Event::DocumentStart, mark))
+                Ok((Event::DocumentStart(true), mark))
             }
             Token(span, _) => Err(ScanError::new_str(
                 span.start,
diff --git a/parser/tests/basic.rs b/parser/tests/basic.rs
index 9782a32..010b1cb 100644
--- a/parser/tests/basic.rs
+++ b/parser/tests/basic.rs
@@ -45,7 +45,7 @@ fn test_empty_doc() {
         run_parser("---").unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(true),
             Event::Scalar("~".to_string(), TScalarStyle::Plain, 0, None),
             Event::DocumentEnd,
             Event::StreamEnd,
@@ -59,7 +59,7 @@ fn test_utf() {
         run_parser("a: 你好").unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::MappingStart(0, None),
             Event::Scalar("a".to_string(), TScalarStyle::Plain, 0, None),
             Event::Scalar("你好".to_string(), TScalarStyle::Plain, 0, None),
@@ -83,7 +83,7 @@ a: b # This is another comment
         run_parser(s).unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::MappingStart(0, None),
             Event::Scalar("a".to_string(), TScalarStyle::Plain, 0, None),
             Event::Scalar("b".to_string(), TScalarStyle::Plain, 0, None),
@@ -106,7 +106,7 @@ fn test_quoting() {
         run_parser(s).unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::SequenceStart(0, None),
             Event::Scalar("plain".to_string(), TScalarStyle::Plain, 0, None),
             Event::Scalar("squote".to_string(), TScalarStyle::SingleQuoted, 0, None),
@@ -131,13 +131,13 @@ a scalar
         run_parser(s).unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::Scalar("a scalar".to_string(), TScalarStyle::Plain, 0, None),
             Event::DocumentEnd,
-            Event::DocumentStart,
+            Event::DocumentStart(true),
             Event::Scalar("a scalar".to_string(), TScalarStyle::Plain, 0, None),
             Event::DocumentEnd,
-            Event::DocumentStart,
+            Event::DocumentStart(true),
             Event::Scalar("a scalar".to_string(), TScalarStyle::Plain, 0, None),
             Event::DocumentEnd,
             Event::StreamEnd,
@@ -152,7 +152,7 @@ fn test_github_27() {
         run_parser("&a").unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::Scalar(String::new(), TScalarStyle::Plain, 1, None),
             Event::DocumentEnd,
             Event::StreamEnd,
@@ -194,7 +194,7 @@ foobar";
         run_parser(s).unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(true),
             Event::Scalar("foobar".to_string(), TScalarStyle::Plain, 0, None),
             Event::DocumentEnd,
             Event::StreamEnd,
@@ -218,7 +218,7 @@ a: |-
         run_parser(s).unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::MappingStart(0, None),
             Event::Scalar("a".to_string(), TScalarStyle::Plain, 0, None),
             Event::Scalar("a\n    b".to_string(), TScalarStyle::Literal, 0, None),
@@ -236,7 +236,7 @@ fn test_bad_docstart() {
         run_parser("----").unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::Scalar("----".to_string(), TScalarStyle::Plain, 0, None),
             Event::DocumentEnd,
             Event::StreamEnd,
@@ -247,7 +247,7 @@ fn test_bad_docstart() {
         run_parser("--- #comment").unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(true),
             Event::Scalar("~".to_string(), TScalarStyle::Plain, 0, None),
             Event::DocumentEnd,
             Event::StreamEnd,
@@ -258,7 +258,7 @@ fn test_bad_docstart() {
         run_parser("---- #comment").unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::Scalar("----".to_string(), TScalarStyle::Plain, 0, None),
             Event::DocumentEnd,
             Event::StreamEnd,
diff --git a/parser/tests/issues.rs b/parser/tests/issues.rs
index ce7c6df..8197a56 100644
--- a/parser/tests/issues.rs
+++ b/parser/tests/issues.rs
@@ -34,7 +34,7 @@ fn test_issue1() {
 
     let expected = [
         Event::StreamStart,
-        Event::DocumentStart,
+        Event::DocumentStart(false),
         Event::SequenceStart(0, None),
         Event::MappingStart(0, None),
         Event::Scalar("a".to_string(), TScalarStyle::Plain, 0, None),
@@ -57,7 +57,7 @@ fn test_issue1() {
         run_parser("[foo: [bar]]: baz").unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::MappingStart(0, None),
             Event::SequenceStart(0, None),
             Event::MappingStart(0, None),
@@ -79,7 +79,7 @@ fn test_issue1() {
         run_parser("[:]").unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::SequenceStart(0, None),
             Event::MappingStart(0, None),
             Event::Scalar("~".to_string(), TScalarStyle::Plain, 0, None),
@@ -96,7 +96,7 @@ fn test_issue1() {
         run_parser("[: [:]]").unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::SequenceStart(0, None),
             Event::MappingStart(0, None),
             Event::Scalar("~".to_string(), TScalarStyle::Plain, 0, None),
@@ -123,7 +123,7 @@ fn test_issue1() {
         // third nested sequences, but not the second.
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::SequenceStart(0, None),
             Event::MappingStart(0, None),
             Event::Scalar("a".to_string(), TScalarStyle::Plain, 0, None),
@@ -153,7 +153,7 @@ fn test_issue1() {
         run_parser(r#"["a":[]]"#).unwrap(),
         [
             Event::StreamStart,
-            Event::DocumentStart,
+            Event::DocumentStart(false),
             Event::SequenceStart(0, None),
             Event::MappingStart(0, None),
             Event::Scalar("a".to_string(), TScalarStyle::DoubleQuoted, 0, None),
diff --git a/parser/tests/spec_test.rs b/parser/tests/spec_test.rs
index bdf36b0..4d2876e 100644
--- a/parser/tests/spec_test.rs
+++ b/parser/tests/spec_test.rs
@@ -26,7 +26,7 @@ struct YamlChecker {
 impl EventReceiver for YamlChecker {
     fn on_event(&mut self, ev: Event) {
         let tev = match ev {
-            Event::DocumentStart => TestEvent::OnDocumentStart,
+            Event::DocumentStart(_) => TestEvent::OnDocumentStart,
             Event::DocumentEnd => TestEvent::OnDocumentEnd,
             Event::SequenceStart(..) => TestEvent::OnSequenceStart,
             Event::SequenceEnd => TestEvent::OnSequenceEnd,
diff --git a/parser/tests/yaml-test-suite.rs b/parser/tests/yaml-test-suite.rs
index 276581f..5521433 100644
--- a/parser/tests/yaml-test-suite.rs
+++ b/parser/tests/yaml-test-suite.rs
@@ -142,7 +142,7 @@ impl EventReceiver for EventReporter {
             Event::StreamStart => "+STR".into(),
             Event::StreamEnd => "-STR".into(),
 
-            Event::DocumentStart => "+DOC".into(),
+            Event::DocumentStart(_) => "+DOC".into(),
             Event::DocumentEnd => "-DOC".into(),
 
             Event::SequenceStart(idx, tag) => {