diff --git a/doc/C09_TutorialSparse.dox b/doc/C09_TutorialSparse.dox
index 20671f57b..6a16c3ae2 100644
--- a/doc/C09_TutorialSparse.dox
+++ b/doc/C09_TutorialSparse.dox
@@ -211,7 +211,7 @@ Here is a typical usage example:
 \code
 typedef Eigen::Triplet<double> T;
 std::vector<T> tripletList;
-triplets.reserve(estimation_of_entries);
+tripletList.reserve(estimation_of_entries);
 for(...)
 {
   // ...