diff --git a/doc/C09_TutorialSparse.dox b/doc/C09_TutorialSparse.dox
index 6022cc514..cf0baa559 100644
--- a/doc/C09_TutorialSparse.dox
+++ b/doc/C09_TutorialSparse.dox
@@ -157,7 +157,7 @@ For instance, the cost of inserting nnz non zeros in a a single purely random in
 A typical scenario to insert nonzeros is illustrated bellow:
 \code
 1: SparseMatrix<double> mat(rows,cols);         // default is column major
-2: mat.reserve(VectorXi::Constant(rows,6));
+2: mat.reserve(VectorXi::Constant(cols,6));
 3: for each i,j such that v_ij != 0
 4:   mat.insert(i,j) = v_ij;                    // alternative: mat.coeffRef(i,j) += v_ij;
 5: mat.makeCompressed();                        // optional