diff --git a/gtsam/nonlinear/NonlinearConjugateGradientOptimizer.h b/gtsam/nonlinear/NonlinearConjugateGradientOptimizer.h
index f9cd22361..63ec4f6ea 100644
--- a/gtsam/nonlinear/NonlinearConjugateGradientOptimizer.h
+++ b/gtsam/nonlinear/NonlinearConjugateGradientOptimizer.h
@@ -40,7 +40,7 @@ class GTSAM_EXPORT NonlinearConjugateGradientOptimizer
 
  protected:
   Parameters params_;
-  DirectionMethod directionMethod_;
+  DirectionMethod directionMethod_ = DirectionMethod::PolakRibiere;
 
   const NonlinearOptimizerParams &_params() const override { return params_; }