diff --git a/gtsam/base/Matrix.cpp b/gtsam/base/Matrix.cpp
index e11263d3b..1369f13b8 100644
--- a/gtsam/base/Matrix.cpp
+++ b/gtsam/base/Matrix.cpp
@@ -248,11 +248,12 @@ istream& operator>>(istream& inputStream, Matrix& destinationMatrix) {
     coeffs.push_back(vector<double>());
     if(!first)
       coeffs.back().reserve(width);
-    std::copy(istream_iterator<double>(stringstream(line)), istream_iterator<double>(),
+    stringstream lineStream(line);
+    std::copy(istream_iterator<double>(lineStream), istream_iterator<double>(),
       back_insert_iterator<vector<double> >(coeffs.back()));
     if(first)
       width = coeffs.back().size();
-    if(coeffs.size() != width)
+    if(coeffs.back().size() != width)
       throw runtime_error("Error reading matrix from input stream, inconsistent numbers of elements in rows");
     ++ height;
   }
@@ -262,7 +263,10 @@ istream& operator>>(istream& inputStream, Matrix& destinationMatrix) {
   int row = 0;
   BOOST_FOREACH(const vector<double>& rowVec, coeffs) {
     destinationMatrix.row(row) = Eigen::Map<const Eigen::RowVectorXd>(&rowVec[0], width);
+    ++ row;
   }
+
+  return inputStream;
 }
 
 /* ************************************************************************* */
diff --git a/gtsam/base/Matrix.h b/gtsam/base/Matrix.h
index 2c13ee7d4..e113e4cf1 100644
--- a/gtsam/base/Matrix.h
+++ b/gtsam/base/Matrix.h
@@ -188,7 +188,7 @@ void save(const Matrix& A, const std::string &s, const std::string& filename);
  * tab-, space-, or comma-separated, similar to the format read by the MATLAB
  * dlmread command.
  */
-istream& operator>>(istream& inputStream, Matrix& destinationMatrix);
+std::istream& operator>>(std::istream& inputStream, Matrix& destinationMatrix);
 
 /**
  * extract submatrix, slice semantics, i.e. range = [i1,i2[ excluding i2