diff --git a/goyaml.v2/patch_test.go b/goyaml.v2/patch_test.go
new file mode 100644
index 0000000..d82655d
--- /dev/null
+++ b/goyaml.v2/patch_test.go
@@ -0,0 +1,23 @@
+package yaml_test
+
+import (
+	"testing"
+
+	yaml "sigs.k8s.io/yaml/goyaml.v2"
+)
+
+func TestIssue117(t *testing.T) {
+	data := []byte(`
+a:
+<<:
+-
+?
+-
+`)
+
+	x := map[string]interface{}{}
+	err := yaml.Unmarshal([]byte(data), &x)
+	if err == nil {
+		t.Errorf("expected error, got none")
+	}
+}
diff --git a/goyaml.v3/decode.go b/goyaml.v3/decode.go
index 0173b69..02e2b17 100644
--- a/goyaml.v3/decode.go
+++ b/goyaml.v3/decode.go
@@ -832,10 +832,10 @@ func (d *decoder) mapping(n *Node, out reflect.Value) (good bool) {
 		if d.unmarshal(n.Content[i], k) {
 			if mergedFields != nil {
 				ki := k.Interface()
-				if mergedFields[ki] {
+				if d.getPossiblyUnhashableKey(mergedFields, ki) {
 					continue
 				}
-				mergedFields[ki] = true
+				d.setPossiblyUnhashableKey(mergedFields, ki, true)
 			}
 			kkind := k.Kind()
 			if kkind == reflect.Interface {
@@ -956,6 +956,24 @@ func failWantMap() {
 	failf("map merge requires map or sequence of maps as the value")
 }
 
+func (d *decoder) setPossiblyUnhashableKey(m map[interface{}]bool, key interface{}, value bool) {
+	defer func() {
+		if err := recover(); err != nil {
+			failf("%v", err)
+		}
+	}()
+	m[key] = value
+}
+
+func (d *decoder) getPossiblyUnhashableKey(m map[interface{}]bool, key interface{}) bool {
+	defer func() {
+		if err := recover(); err != nil {
+			failf("%v", err)
+		}
+	}()
+	return m[key]
+}
+
 func (d *decoder) merge(parent *Node, merge *Node, out reflect.Value) {
 	mergedFields := d.mergedFields
 	if mergedFields == nil {
@@ -963,7 +981,7 @@ func (d *decoder) merge(parent *Node, merge *Node, out reflect.Value) {
 		for i := 0; i < len(parent.Content); i += 2 {
 			k := reflect.New(ifaceType).Elem()
 			if d.unmarshal(parent.Content[i], k) {
-				d.mergedFields[k.Interface()] = true
+				d.setPossiblyUnhashableKey(d.mergedFields, k.Interface(), true)
 			}
 		}
 	}
diff --git a/goyaml.v3/patch_test.go b/goyaml.v3/patch_test.go
index 7220301..3b76276 100644
--- a/goyaml.v3/patch_test.go
+++ b/goyaml.v3/patch_test.go
@@ -18,6 +18,7 @@ package yaml_test
 
 import (
 	"bytes"
+	"testing"
 
 	. "gopkg.in/check.v1"
 	yaml "sigs.k8s.io/yaml/goyaml.v3"
@@ -158,3 +159,19 @@ func (s *S) TestNewLinePreserved(c *C) {
 	// the newline at the start of the file should be preserved
 	c.Assert(string(data), Equals, "_: |4\n\n    a:\n            b:\n                    c: d\n")
 }
+
+func TestIssue117(t *testing.T) {
+	data := []byte(`
+a:
+<<:
+-
+?
+-
+`)
+
+	x := map[string]interface{}{}
+	err := yaml.Unmarshal([]byte(data), &x)
+	if err == nil {
+		t.Errorf("expected error, got none")
+	}
+}