diff --git a/fieldpath/element.go b/fieldpath/element.go
index 5d767081..9783c3ba 100644
--- a/fieldpath/element.go
+++ b/fieldpath/element.go
@@ -163,12 +163,8 @@ func (s *PathElementSet) Insert(pe PathElement) {
 	if s.members[loc].Equals(pe) {
 		return
 	}
-	n := len(s.members) - 1
-	s.members = append(s.members, s.members[n])
-	for n > loc {
-		s.members[n] = s.members[n-1]
-		n--
-	}
+	s.members = append(s.members, PathElement{})
+	copy(s.members[loc+1:], s.members[loc:])
 	s.members[loc] = pe
 }
 
diff --git a/fieldpath/set.go b/fieldpath/set.go
index 9d0b803b..b3aebfef 100644
--- a/fieldpath/set.go
+++ b/fieldpath/set.go
@@ -188,12 +188,8 @@ func (s *SetNodeMap) Descend(pe PathElement) *Set {
 	if s.members[loc].pathElement.Equals(pe) {
 		return s.members[loc].set
 	}
-	n := len(s.members) - 1
-	s.members = append(s.members, s.members[n])
-	for n > loc {
-		s.members[n] = s.members[n-1]
-		n--
-	}
+	s.members = append(s.members, setNode{})
+	copy(s.members[loc+1:], s.members[loc:])
 	s.members[loc] = setNode{pathElement: pe, set: &Set{}}
 	return s.members[loc].set
 }