diff --git a/src/nnls.cpp b/src/nnls.cpp
index 1cb30db..bb975f6 100644
--- a/src/nnls.cpp
+++ b/src/nnls.cpp
@@ -2,7 +2,7 @@
 #include <RcppArmadillo.h>
 
 // [[Rcpp::export]]
-arma::Mat<double> c_nnls_double(const arma::mat& x, const arma::vec& y, uint max_iter,
+arma::Mat<double> c_nnls_double(const arma::mat& x, const arma::vec& y, unsigned int max_iter,
                                 double rel_tol) {
   auto n = y.size();
   Rcpp::NumericVector res(n);