diff --git a/gtsam/base/timing.cpp b/gtsam/base/timing.cpp
index ba784ffab..c16138cef 100644
--- a/gtsam/base/timing.cpp
+++ b/gtsam/base/timing.cpp
@@ -172,6 +172,7 @@ void TimingOutline::toc() {
   assert(timerActive_);
   double elapsed = timer_.elapsed();
   add(size_t(elapsed * 1000000.0));
+  *timerActive_ = false;
 #endif
 }