diff --git a/gtsam.h b/gtsam.h
index 05cf7ffb5..261a962d0 100644
--- a/gtsam.h
+++ b/gtsam.h
@@ -1725,6 +1725,7 @@ class KeySet {
 
   // structure specific methods
   void insert(size_t key);
+  void merge(gtsam::KeySet& other);
   bool erase(size_t key); // returns true if value was removed
   bool count(size_t key) const; // returns true if value exists
 
diff --git a/gtsam/base/FastSet.h b/gtsam/base/FastSet.h
index 7ed6c7cd7..69e841e57 100644
--- a/gtsam/base/FastSet.h
+++ b/gtsam/base/FastSet.h
@@ -103,6 +103,11 @@ public:
   /** Check for equality within tolerance to implement Testable */
   bool equals(const FastSet<VALUE>& other, double tol = 1e-9) const { return FastSetTestableHelper<VALUE>::equals(*this, other, tol); }
 
+  /** insert another set: handy for MATLAB access */
+  void merge(const FastSet& other) {
+    Base::insert(other.begin(),other.end());
+  }
+
 private:
   /** Serialization function */
   friend class boost::serialization::access;