diff --git a/gtsam_unstable/nonlinear/tests/testIncrementalFixedLagSmoother.cpp b/gtsam/nonlinear/tests/testIncrementalFixedLagSmoother.cpp
similarity index 99%
rename from gtsam_unstable/nonlinear/tests/testIncrementalFixedLagSmoother.cpp
rename to gtsam/nonlinear/tests/testIncrementalFixedLagSmoother.cpp
index 269177b5d..a31f3646f 100644
--- a/gtsam_unstable/nonlinear/tests/testIncrementalFixedLagSmoother.cpp
+++ b/gtsam/nonlinear/tests/testIncrementalFixedLagSmoother.cpp
@@ -30,7 +30,7 @@
 #include <gtsam/slam/BetweenFactor.h>
 #include <gtsam/slam/PriorFactor.h>
 #include <gtsam/slam/dataset.h>  // For writeG2o
-#include <gtsam_unstable/nonlinear/IncrementalFixedLagSmoother.h>
+#include <gtsam/nonlinear/IncrementalFixedLagSmoother.h>
 
 #include <CppUnitLite/TestHarness.h>