diff --git a/NEWS.md b/NEWS.md
index f93058a..b51d9df 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -16,8 +16,9 @@ Development release.
 ## Bug fixes
 
 - Added a missing `@family` tag to the `pcens` functions. This omission resulted in the Weibull analytical solution not being visible in the package documentation.
-- Added precalculation of vector sizes to the `primarycensored_cdf()` stan function, avoiding errors on some platforms due to narrowing conversions in aggregate initialisation. 
+- Added precalculation of vector sizes to the `primarycensored_cdf()` stan function, avoiding errors on some platforms due to narrowing conversions in aggregate initialisation.
 - Changed `D` to be of type real in `pcens_model.stan` in order to support infinite `relative_obs_time`.
+- Switched to using `num_elements()` over `size()` in all stan code to resolve compilation issues on some platforms as reported by @sbfnk.
 
 # primarycensored 1.0.0
 
diff --git a/inst/stan/functions/primarycensored.stan b/inst/stan/functions/primarycensored.stan
index 30447f8..37e3e77 100644
--- a/inst/stan/functions/primarycensored.stan
+++ b/inst/stan/functions/primarycensored.stan
@@ -37,8 +37,8 @@ real primarycensored_cdf(data real d, int dist_id, array[] real params,
   } else {
     // Use numerical integration for other cases
     real lower_bound = max({d - pwindow, 1e-6});
-    int n_params = size(params);
-    int n_primary_params = size(primary_params);
+    int n_params = num_elements(params);
+    int n_primary_params = num_elements(primary_params);
     array[n_params + n_primary_params] real theta = append_array(params, primary_params);
     array[4] int ids = {dist_id, primary_id, n_params, n_primary_params};
 
diff --git a/inst/stan/functions/primarycensored_ode.stan b/inst/stan/functions/primarycensored_ode.stan
index 1df06a2..b2adf94 100644
--- a/inst/stan/functions/primarycensored_ode.stan
+++ b/inst/stan/functions/primarycensored_ode.stan
@@ -100,7 +100,7 @@ vector primarycensored_ode(real t, vector y, array[] real theta,
   }
   array[primary_params_len] real primary_params;
   if (primary_params_len) {
-    int primary_loc = size(theta);
+    int primary_loc = num_elements(theta);
     primary_params = theta[primary_loc - primary_params_len + 1:primary_loc];
   }