diff --git a/js/src/jsstr.cpp b/js/src/jsstr.cpp
index c2ff66718..a13cf97e9 100644
--- a/js/src/jsstr.cpp
+++ b/js/src/jsstr.cpp
@@ -1372,7 +1372,8 @@ class StringSegmentRange
 {
     // If malloc() shows up in any profiles from this vector, we can add a new
     // StackAllocPolicy which stashes a reusable freed-at-gc buffer in the cx.
-    Rooted<StringVector> stack;
+    using StackVector = js::TraceableVector<JSString*, 16>;
+    Rooted<StackVector> stack;
     RootedLinearString cur;
 
     bool settle(JSString* str) {
@@ -1388,7 +1389,7 @@ class StringSegmentRange
 
   public:
     explicit StringSegmentRange(JSContext* cx)
-      : stack(cx, StringVector(cx)), cur(cx)
+      : stack(cx, StackVector(cx)), cur(cx)
     {}
 
     MOZ_WARN_UNUSED_RESULT bool init(JSString* str) {