diff --git a/gtsam_unstable/slam/CombinedImuFactor.h b/gtsam_unstable/slam/CombinedImuFactor.h
index 0a7fb270c..1879802da 100644
--- a/gtsam_unstable/slam/CombinedImuFactor.h
+++ b/gtsam_unstable/slam/CombinedImuFactor.h
@@ -341,7 +341,7 @@ namespace gtsam {
   public:
 
     /** Shorthand for a smart pointer to a factor */
-    typedef boost::shared_ptr<CombinedImuFactor> shared_ptr;
+    typedef typename boost::shared_ptr<CombinedImuFactor> shared_ptr;
 
     /** Default constructor - only use for serialization */
     CombinedImuFactor() : preintegratedMeasurements_(imuBias::ConstantBias(), Matrix3::Zero(), Matrix3::Zero(), Matrix3::Zero(), Matrix3::Zero(), Matrix3::Zero(), Matrix::Zero(6,6)) {}
diff --git a/gtsam_unstable/slam/ImuFactor.h b/gtsam_unstable/slam/ImuFactor.h
index 8ba169770..4a8a84b6d 100644
--- a/gtsam_unstable/slam/ImuFactor.h
+++ b/gtsam_unstable/slam/ImuFactor.h
@@ -304,7 +304,7 @@ namespace gtsam {
   public:
 
     /** Shorthand for a smart pointer to a factor */
-    typedef boost::shared_ptr<ImuFactor> shared_ptr;
+    typedef typename boost::shared_ptr<ImuFactor> shared_ptr;
 
     /** Default constructor - only use for serialization */
     ImuFactor() : preintegratedMeasurements_(imuBias::ConstantBias(), Matrix3::Zero(), Matrix3::Zero(), Matrix3::Zero()) {}