diff --git a/src/compile.cpp b/src/compile.cpp
index 3844abf78e..57b2966b1c 100644
--- a/src/compile.cpp
+++ b/src/compile.cpp
@@ -5053,8 +5053,6 @@ class MyProcessor: public Processor {
       Visitor(MyThread* t, MyThread* target): t(t), target(target) { }
 
       virtual void visit(void* ip, void* base, void* stack) {
-        ensure(t, traceSize(target));
-
         void* oldIp = target->ip;
         void* oldBase = target->base;
         void* oldStack = target->stack;
@@ -5090,6 +5088,8 @@ class MyProcessor: public Processor {
           }
         }
 
+        ensure(t, traceSize(target));
+
         t->tracing = true;
         trace = makeTrace(t, target);
         t->tracing = false;