Fix warning.

1 files changed, 1 insertions, 1 deletions

diff --git a/doc/special_examples/random_cpp11.cpp b/doc/special_examples/random_cpp11.cpp
index ccd7c77d0..adc3c110c 100644
--- a/doc/special_examples/random_cpp11.cpp
+++ b/doc/special_examples/random_cpp11.cpp
@@ -7,7 +7,7 @@ using namespace Eigen;
 int main() {
   std::default_random_engine generator;
   std::poisson_distribution<int> distribution(4.1);
-  auto poisson = [&] (int) {return distribution(generator);};
+  auto poisson = [&] (Eigen::Index) {return distribution(generator);};
 
   RowVectorXi v = RowVectorXi::NullaryExpr(10, poisson );
   std::cout << v << "\n";