diff --git a/DESCRIPTION b/DESCRIPTION
index cc58522..dc41bc5 100755
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -13,7 +13,7 @@ LazyData: true
 ByteCompile: true
 Depends: R (>= 3.5.0), methods,Rcpp (>= 1.0.0)
 Imports: 
-  rstan (>= 2.18.2), 
+  rstan (>= 2.26.0), 
   rstantools (>= 2.3.0), 
   magrittr (>= 1.5), 
   dplyr (>= 0.8.0), 
@@ -21,8 +21,8 @@ Imports:
   purrr (>= 0.3.0), 
   ggplot2 (>= 2.2.1)
 LinkingTo: 
-  StanHeaders (>= 2.18.1), 
-  rstan (>= 2.18.2), 
+  StanHeaders (>= 2.26.0), 
+  rstan (>= 2.26.0), 
   BH (>= 1.69.0-1), 
   Rcpp (>= 1.0.0), 
   RcppEigen (>= 0.3.3.5.0), 
diff --git a/inst/stan/emax.stan b/inst/stan/emax.stan
index 14ebee2..3f0e8ea 100755
--- a/inst/stan/emax.stan
+++ b/inst/stan/emax.stan
@@ -4,9 +4,9 @@ data{
   vector[N] response;
 
   // Covariates
-  int<lower = 1> covemax[N];
-  int<lower = 1> covec50[N];
-  int<lower = 1> cove0[N];
+  array[N] int<lower = 1> covemax;
+  array[N] int<lower = 1> covec50;
+  array[N] int<lower = 1> cove0;
   int<lower = 1> n_covlev_emax;
   int<lower = 1> n_covlev_ec50;
   int<lower = 1> n_covlev_e0;
@@ -37,10 +37,10 @@ data{
 parameters{
   // vector[n_covlev_emax] emax;
   vector<lower = 0>[n_covlev_ec50] ec50;
-  // vector[n_covlev_e0] e0_par[1-e0_fix_flg];
-  real e0_par[n_covlev_e0, 1-e0_fix_flg];
-  real emax_par[n_covlev_emax, 1-emax_fix_flg];
-  real<lower = 0> gamma_par[1-gamma_fix_flg];
+  // array[1-e0_fix_flg] vector[n_covlev_e0] e0_par;
+  array[n_covlev_e0, 1-e0_fix_flg] real e0_par;
+  array[n_covlev_emax, 1-emax_fix_flg] real emax_par;
+  array[1-gamma_fix_flg] real<lower = 0> gamma_par;
 
   real<lower = 0> sigma;
 }