diff --git a/decode_test.go b/decode_test.go
index 4ec7893c..8239623f 100644
--- a/decode_test.go
+++ b/decode_test.go
@@ -606,6 +606,19 @@ var unmarshalTests = []struct {
 		&struct{ B []int }{[]int{1, 2}},
 	},
 
+	// Bug https://github.com/yaml/go-yaml/issues/109
+	{
+		// alias must be followed by a space in mapping node
+		"foo: &bar bar\n*bar : quz\n",
+		map[string]any{"foo": "bar", "bar": "quz"},
+	},
+
+	{
+		// alias can contain various characters specified by the YAML specification
+		"foo: &b./ar bar\n*b./ar : quz\n",
+		map[string]any{"foo": "bar", "bar": "quz"},
+	},
+
 	// Bug #1133337
 	{
 		"foo: ''",
@@ -1111,6 +1124,9 @@ var unmarshalErrorTests = []struct {
 	{"a: 1\nb: 2\nc 2\nd: 3\n", "^yaml: line 3: could not find expected ':'$"},
 	{"#\n-\n{", "yaml: line 3: could not find expected ':'"},   // Issue #665
 	{"0: [:!00 \xef", "yaml: incomplete UTF-8 octet sequence"}, // Issue #666
+	// anchor cannot contain a colon
+	// https://github.com/yaml/go-yaml/issues/109
+	{"foo: &bar: bar\n*bar: : quz\n", "^yaml: mapping values are not allowed in this context$"},
 	{
 		"a: &a [00,00,00,00,00,00,00,00,00]\n" +
 			"b: &b [*a,*a,*a,*a,*a,*a,*a,*a,*a]\n" +
diff --git a/emitterc.go b/emitterc.go
index aaf37746..4e6e497f 100644
--- a/emitterc.go
+++ b/emitterc.go
@@ -813,7 +813,16 @@ func (emitter *yamlEmitter) emitBlockMappingKey(event *yamlEvent, first bool) bo
 	}
 	if emitter.checkSimpleKey() {
 		emitter.states = append(emitter.states, yaml_EMIT_BLOCK_MAPPING_SIMPLE_VALUE_STATE)
-		return emitter.emitNode(event, false, false, true, true)
+		if !emitter.emitNode(event, false, false, true, true) {
+			return false
+		}
+
+		if event.typ == yaml_ALIAS_EVENT {
+			// make sure there's a space after the alias
+			return emitter.put(' ')
+		}
+
+		return true
 	}
 	if !emitter.writeIndicator([]byte{'?'}, true, false, true) {
 		return false
diff --git a/node_test.go b/node_test.go
index 9a0394ab..836463b2 100644
--- a/node_test.go
+++ b/node_test.go
@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"reflect"
 	"strings"
 	"testing"
 
@@ -1129,7 +1130,7 @@ var nodeTests = []struct {
 			}},
 		},
 	}, {
-		"a: &anchor(.!@#$%^&*+=?:;)name [1, 2]\nb: *anchor(.!@#$%^&*+=?:;)name\n",
+		"a: &anchor(.!@#$%^&*+=?;)name [1, 2]\nb: *anchor(.!@#$%^&*+=?;)name\n",
 		yaml.Node{
 			Kind:   yaml.DocumentNode,
 			Line:   1,
@@ -1147,11 +1148,11 @@ var nodeTests = []struct {
 						Line:   1,
 						Column: 1,
 					},
-					saveNode("anchor(.!@#$%^&*+=?:;)name", &yaml.Node{
+					saveNode("anchor(.!@#$%^&*+=?;)name", &yaml.Node{
 						Kind:   yaml.SequenceNode,
 						Style:  yaml.FlowStyle,
 						Tag:    "!!seq",
-						Anchor: "anchor(.!@#$%^&*+=?:;)name",
+						Anchor: "anchor(.!@#$%^&*+=?;)name",
 						Line:   1,
 						Column: 4,
 						Content: []*yaml.Node{{
@@ -1159,13 +1160,13 @@ var nodeTests = []struct {
 							Value:  "1",
 							Tag:    "!!int",
 							Line:   1,
-							Column: 33,
+							Column: 32,
 						}, {
 							Kind:   yaml.ScalarNode,
 							Value:  "2",
 							Tag:    "!!int",
 							Line:   1,
-							Column: 36,
+							Column: 35,
 						}},
 					}),
 					{
@@ -1177,14 +1178,58 @@ var nodeTests = []struct {
 					},
 					{
 						Kind:   yaml.AliasNode,
-						Value:  "anchor(.!@#$%^&*+=?:;)name",
-						Alias:  dropNode("anchor(.!@#$%^&*+=?:;)name"),
+						Value:  "anchor(.!@#$%^&*+=?;)name",
+						Alias:  dropNode("anchor(.!@#$%^&*+=?;)name"),
 						Line:   2,
 						Column: 4,
 					},
 				},
 			}},
 		},
+	}, {
+		"a: &x 1\n*x : c\n",
+		yaml.Node{
+			Kind:   yaml.DocumentNode,
+			Line:   1,
+			Column: 1,
+			Content: []*yaml.Node{{
+				Kind:   yaml.MappingNode,
+				Line:   1,
+				Column: 1,
+				Tag:    "!!map",
+				Content: []*yaml.Node{
+					{
+						Kind:   yaml.ScalarNode,
+						Value:  "a",
+						Tag:    "!!str",
+						Line:   1,
+						Column: 1,
+					},
+					saveNode("x", &yaml.Node{
+						Kind:   yaml.ScalarNode,
+						Value:  "1",
+						Tag:    "!!int",
+						Anchor: "x",
+						Line:   1,
+						Column: 4,
+					}),
+					{
+						Kind:   yaml.AliasNode,
+						Value:  "x",
+						Alias:  dropNode("x"),
+						Line:   2,
+						Column: 1,
+					},
+					{
+						Kind:   yaml.ScalarNode,
+						Value:  "c",
+						Tag:    "!!str",
+						Line:   2,
+						Column: 6,
+					},
+				},
+			}},
+		},
 	}, {
 		"# One\n# Two\ntrue # Three\n# Four\n# Five\n",
 		yaml.Node{
@@ -2756,53 +2801,125 @@ func TestNodeRoundtrip(t *testing.T) {
 	defer os.Setenv("TZ", os.Getenv("TZ"))
 	os.Setenv("TZ", "UTC")
 	for i, item := range nodeTests {
-		t.Logf("test %d: %q", i, item.yaml)
+		t.Run(fmt.Sprintf("test %d", i), func(t *testing.T) {
+			t.Logf("test %d: %q", i, item.yaml)
+			if strings.Contains(item.yaml, "#") {
+				var buf bytes.Buffer
+				fprintComments(&buf, &item.node, "    ")
+				t.Logf("  expected comments:\n%s", buf.Bytes())
+			}
 
-		if strings.Contains(item.yaml, "#") {
-			var buf bytes.Buffer
-			fprintComments(&buf, &item.node, "    ")
-			t.Logf("  expected comments:\n%s", buf.Bytes())
-		}
+			decode := true
+			encode := true
 
-		decode := true
-		encode := true
+			testYaml := item.yaml
+			if s := strings.TrimPrefix(testYaml, "[decode]"); s != testYaml {
+				encode = false
+				testYaml = s
+			}
+			if s := strings.TrimPrefix(testYaml, "[encode]"); s != testYaml {
+				decode = false
+				testYaml = s
+			}
 
-		testYaml := item.yaml
-		if s := strings.TrimPrefix(testYaml, "[decode]"); s != testYaml {
-			encode = false
-			testYaml = s
-		}
-		if s := strings.TrimPrefix(testYaml, "[encode]"); s != testYaml {
-			decode = false
-			testYaml = s
-		}
+			if decode {
+				var node yaml.Node
+				err := yaml.Unmarshal([]byte(testYaml), &node)
+				assert.NoError(t, err)
+				if strings.Contains(item.yaml, "#") {
+					var buf bytes.Buffer
+					fprintComments(&buf, &node, "    ")
+					t.Logf("  obtained comments:\n%s", buf.Bytes())
+				}
 
-		if decode {
-			var node yaml.Node
-			err := yaml.Unmarshal([]byte(testYaml), &node)
-			assert.NoError(t, err)
-			if strings.Contains(item.yaml, "#") {
-				var buf bytes.Buffer
-				fprintComments(&buf, &node, "    ")
-				t.Logf("  obtained comments:\n%s", buf.Bytes())
+				assertNodeEqual(t, &item.node, &node)
 			}
-			assert.DeepEqual(t, &item.node, &node)
+			if encode {
+				node := deepCopyNode(&item.node, nil)
+				buf := bytes.Buffer{}
+				enc := yaml.NewEncoder(&buf)
+				enc.SetIndent(2)
+				err := enc.Encode(node)
+				assert.NoError(t, err)
+				err = enc.Close()
+				assert.NoError(t, err)
+				assert.Equal(t, buf.String(), testYaml)
+
+				// Ensure there were no mutations to the tree.
+				assertNodeEqual(t, &item.node, node)
+			}
+		})
+	}
+}
+
+// assertNodeEqual is a helper to check whether two YAML nodes are equal.
+func assertNodeEqual(t *testing.T, want *yaml.Node, got *yaml.Node) {
+	t.Helper()
+
+	if reflect.DeepEqual(got, want) {
+		// fast path
+		return
+	}
+
+	if got.Tag != want.Tag {
+		t.Errorf("Tag mismatch: want: %q got: %q", want.Tag, got.Tag)
+	}
+
+	if got.Kind != want.Kind {
+		t.Errorf("Kind mismatch: want: %q got: %q", want.Kind, got.Kind)
+	}
+
+	if got.Style != want.Style {
+		t.Errorf("Style mismatch: want: %q got: %q", want.Style, got.Style)
+	}
+
+	if got.HeadComment != want.HeadComment {
+		t.Errorf("HeadComment mismatch: want: %#v got: %#v", want.HeadComment, got.HeadComment)
+	}
+
+	if got.LineComment != want.LineComment {
+		t.Errorf("LineComment mismatch: want: %#v got: %#v", want.LineComment, got.LineComment)
+	}
+
+	if got.FootComment != want.FootComment {
+		t.Errorf("FootComment mismatch: want: %#v got: %#v", want.FootComment, got.FootComment)
+	}
+
+	if got.Value != want.Value {
+		t.Errorf("Value mismatch: want: %q got: %q", want.Value, got.Value)
+	}
+
+	if got.Anchor != want.Anchor {
+		t.Errorf("Anchor mismatch: want: %q got: %q", want.Anchor, got.Anchor)
+	}
+
+	if got.Line != want.Line {
+		t.Errorf("Line mismatch: want: %d got: %d", want.Line, got.Line)
+	}
+
+	if got.Column != want.Column {
+		t.Errorf("Column mismatch: want: %d got: %d", want.Column, got.Column)
+	}
+
+	if !reflect.DeepEqual(got.Content, want.Content) {
+		// Content differs
+
+		if len(got.Content) != len(want.Content) {
+			t.Errorf("Content length mismatch:\nwant: %d\ngot: %d", len(want.Content), len(got.Content))
 		}
-		if encode {
-			node := deepCopyNode(&item.node, nil)
-			buf := bytes.Buffer{}
-			enc := yaml.NewEncoder(&buf)
-			enc.SetIndent(2)
-			err := enc.Encode(node)
-			assert.NoError(t, err)
-			err = enc.Close()
-			assert.NoError(t, err)
-			assert.Equal(t, buf.String(), testYaml)
 
-			// Ensure there were no mutations to the tree.
-			assert.DeepEqual(t, &item.node, node)
+		for i := 0; i < len(want.Content) && i < len(got.Content); i++ {
+			assertNodeEqual(t, want.Content[i], got.Content[i])
 		}
 	}
+
+	if t.Failed() {
+		// we already reported an error, there is no need to report it again.
+		return
+	}
+
+	// this error message is harder to read, and is only shown if no other errors were reported.
+	t.Errorf("nodes differ:\nwant:\n%#v\ngot:\n%#v", want, got)
 }
 
 func deepCopyNode(node *yaml.Node, cache map[*yaml.Node]*yaml.Node) *yaml.Node {
@@ -2909,7 +3026,7 @@ func TestSetString(t *testing.T) {
 
 		node.SetString(item.str)
 
-		assert.DeepEqual(t, item.node, node)
+		assertNodeEqual(t, &item.node, &node)
 
 		buf := bytes.Buffer{}
 		enc := yaml.NewEncoder(&buf)
diff --git a/yamlprivateh.go b/yamlprivateh.go
index 58b9a4ee..70d27aac 100644
--- a/yamlprivateh.go
+++ b/yamlprivateh.go
@@ -67,6 +67,18 @@ func isFlowIndicator(b []byte, i int) bool {
 // We further limit it to ascii chars only, which is a subset of the spec
 // production but is usually what most people expect.
 func isAnchorChar(b []byte, i int) bool {
+	if isColon(b, i) {
+		// [Go] we exclude colons from anchor/alias names.
+		//
+		// A colon is a valid anchor character according to the YAML 1.2 specification,
+		// but it can lead to ambiguity.
+		// https://github.com/yaml/go-yaml/issues/109
+		//
+		// Also, it would have been a breaking change to support it, as go.yaml.in/yaml/v3 ignores it.
+		// Supporting it could lead to unexpected behavior.
+		return false
+	}
+
 	return isPrintable(b, i) &&
 		!isLineBreak(b, i) &&
 		!isBlank(b, i) &&
@@ -75,6 +87,11 @@ func isAnchorChar(b []byte, i int) bool {
 		isASCII(b, i)
 }
 
+// isColon checks whether the character at the specified position is a colon.
+func isColon(b []byte, i int) bool {
+	return b[i] == ':'
+}
+
 // Check if the character at the specified position is a digit.
 func isDigit(b []byte, i int) bool {
 	return b[i] >= '0' && b[i] <= '9'
diff --git a/yts/known-failing-tests b/yts/known-failing-tests
index f8e91cff..714438e8 100644
--- a/yts/known-failing-tests
+++ b/yts/known-failing-tests
@@ -4,6 +4,8 @@ TestYAMLSuite/2JQS/UnmarshalTest
 TestYAMLSuite/2JQS/EventComparisonTest
 TestYAMLSuite/2LFX/UnmarshalTest
 TestYAMLSuite/2LFX/EventComparisonTest
+TestYAMLSuite/2SXE/UnmarshalTest
+TestYAMLSuite/2SXE/EventComparisonTest
 TestYAMLSuite/35KP/JSONComparisonTest
 TestYAMLSuite/3HFZ/UnmarshalTest
 TestYAMLSuite/3UYS/UnmarshalTest
@@ -185,6 +187,8 @@ TestYAMLSuite/01#15/UnmarshalTest
 TestYAMLSuite/01#15/EventComparisonTest
 TestYAMLSuite/W4TN/UnmarshalTest
 TestYAMLSuite/W4TN/EventComparisonTest
+TestYAMLSuite/W5VH/UnmarshalTest
+TestYAMLSuite/W5VH/EventComparisonTest
 TestYAMLSuite/WZ62/UnmarshalTest
 TestYAMLSuite/WZ62/EventComparisonTest
 TestYAMLSuite/X38W/UnmarshalTest
@@ -192,6 +196,8 @@ TestYAMLSuite/X38W/EventComparisonTest
 TestYAMLSuite/X4QW/UnmarshalTest
 TestYAMLSuite/X4QW/EventComparisonTest
 TestYAMLSuite/XW4D/UnmarshalTest
+TestYAMLSuite/Y2GN/EventComparisonTest
+TestYAMLSuite/Y2GN/JSONComparisonTest
 TestYAMLSuite/001/UnmarshalTest
 TestYAMLSuite/001/EventComparisonTest
 TestYAMLSuite/003/UnmarshalTest