diff --git a/gtsam/base/Vector.cpp b/gtsam/base/Vector.cpp
index 658ab9a0d4..16d913a967 100644
--- a/gtsam/base/Vector.cpp
+++ b/gtsam/base/Vector.cpp
@@ -299,17 +299,14 @@ weightedPseudoinverse(const Vector& a, const Vector& weights) {
 }
 
 /* ************************************************************************* */
-Vector concatVectors(const std::list<Vector>& vs)
-{
+Vector concatVectors(const std::list<Vector>& vs) {
   size_t dim = 0;
-  for(Vector v: vs)
-  dim += v.size();
+  for (const Vector& v : vs) dim += v.size();
 
   Vector A(dim);
   size_t index = 0;
-  for(Vector v: vs) {
-    for(int d = 0; d < v.size(); d++)
-      A(d+index) = v(d);
+  for (const Vector& v : vs) {
+    for (int d = 0; d < v.size(); d++) A(d + index) = v(d);
     index += v.size();
   }
 
diff --git a/gtsam/linear/NoiseModel.cpp b/gtsam/linear/NoiseModel.cpp
index 8bcef6fcce..7108a7660f 100644
--- a/gtsam/linear/NoiseModel.cpp
+++ b/gtsam/linear/NoiseModel.cpp
@@ -47,8 +47,9 @@ void updateAb(MATRIX& Ab, int j, const Vector& a, const Vector& rd) {
 
 /* ************************************************************************* */
 // check *above the diagonal* for non-zero entries
-boost::optional<Vector> checkIfDiagonal(const Matrix M) {
+boost::optional<Vector> checkIfDiagonal(const Matrix& M) {
   size_t m = M.rows(), n = M.cols();
+  assert(m > 0);
   // check all non-diagonal entries
   bool full = false;
   size_t i, j;
@@ -92,7 +93,7 @@ Gaussian::shared_ptr Gaussian::SqrtInformation(const Matrix& R, bool smart) {
       return Diagonal::Sigmas(diagonal->array().inverse(), true);
   }
   // NOTE(frank): only reaches here if !(smart && diagonal)
-  return shared_ptr(new Gaussian(R.rows(), R));
+  return boost::make_shared<Gaussian>(R.rows(), R);
 }
 
 /* ************************************************************************* */
@@ -108,7 +109,7 @@ Gaussian::shared_ptr Gaussian::Information(const Matrix& information, bool smart
   else {
     Eigen::LLT<Matrix> llt(information);
     Matrix R = llt.matrixU();
-    return shared_ptr(new Gaussian(n, R));
+    return boost::make_shared<Gaussian>(n, R);
   }
 }
 
diff --git a/gtsam/linear/NoiseModel.h b/gtsam/linear/NoiseModel.h
index 5a29e5d7dd..7bcf808e50 100644
--- a/gtsam/linear/NoiseModel.h
+++ b/gtsam/linear/NoiseModel.h
@@ -732,7 +732,7 @@ namespace gtsam {
     };
 
     // Helper function
-    GTSAM_EXPORT boost::optional<Vector> checkIfDiagonal(const Matrix M);
+    GTSAM_EXPORT boost::optional<Vector> checkIfDiagonal(const Matrix& M);
 
   } // namespace noiseModel
 
diff --git a/gtsam/nonlinear/ISAM2Clique.cpp b/gtsam/nonlinear/ISAM2Clique.cpp
index f7a1c14a03..b3dc49342b 100644
--- a/gtsam/nonlinear/ISAM2Clique.cpp
+++ b/gtsam/nonlinear/ISAM2Clique.cpp
@@ -245,7 +245,7 @@ bool ISAM2Clique::optimizeWildfireNode(const KeySet& replaced, double threshold,
 
     // Back-substitute
     fastBackSubstitute(delta);
-    count += conditional_->nrFrontals();
+    *count += conditional_->nrFrontals();
 
     if (valuesChanged(replaced, originalValues, *delta, threshold)) {
       markFrontalsAsChanged(changed);