diff --git a/cmp/cmpopts/ignore.go b/cmp/cmpopts/ignore.go
index 016891d..e86554b 100644
--- a/cmp/cmpopts/ignore.go
+++ b/cmp/cmpopts/ignore.go
@@ -50,7 +50,7 @@ func (tf typeFilter) filter(p cmp.Path) bool {
 	if len(p) < 1 {
 		return false
 	}
-	t := p[len(p)-1].Type()
+	t := p.Last().Type()
 	for _, ti := range tf {
 		if t.AssignableTo(ti) {
 			return true
@@ -95,7 +95,7 @@ func (tf ifaceFilter) filter(p cmp.Path) bool {
 	if len(p) < 1 {
 		return false
 	}
-	t := p[len(p)-1].Type()
+	t := p.Last().Type()
 	for _, ti := range tf {
 		if t.AssignableTo(ti) {
 			return true
@@ -131,14 +131,11 @@ func newUnexportedFilter(typs ...interface{}) unexportedFilter {
 	return ux
 }
 func (xf unexportedFilter) filter(p cmp.Path) bool {
-	if len(p) < 2 {
-		return false
-	}
-	sf, ok := p[len(p)-1].(cmp.StructField)
+	sf, ok := p.Index(-1).(cmp.StructField)
 	if !ok {
 		return false
 	}
-	return xf.m[p[len(p)-2].Type()] && !isExported(sf.Name())
+	return xf.m[p.Index(-2).Type()] && !isExported(sf.Name())
 }
 
 // isExported reports whether the identifier is exported.
diff --git a/cmp/path.go b/cmp/path.go
index 76d73f7..13d9c2e 100644
--- a/cmp/path.go
+++ b/cmp/path.go
@@ -94,10 +94,21 @@ func (pa *Path) pop() {
 // Last returns the last PathStep in the Path.
 // If the path is empty, this returns a non-nil PathStep that reports a nil Type.
 func (pa Path) Last() PathStep {
-	if len(pa) > 0 {
-		return pa[len(pa)-1]
+	return pa.Index(-1)
+}
+
+// Index returns the ith step in the Path and supports negative indexing.
+// A negative index starts counting from the tail of the Path such that -1
+// refers to the last step, -2 refers to the second-to-last step, and so on.
+// If index is invalid, this returns a non-nil PathStep that reports a nil Type.
+func (pa Path) Index(i int) PathStep {
+	if i < 0 {
+		i = len(pa) + i
+	}
+	if i < 0 || i >= len(pa) {
+		return pathStep{}
 	}
-	return pathStep{}
+	return pa[i]
 }
 
 // String returns the simplified path to a node.