diff --git a/rstan/rstan/R/zzz.R b/rstan/rstan/R/zzz.R
index 3f648c594..4cb0fade4 100644
--- a/rstan/rstan/R/zzz.R
+++ b/rstan/rstan/R/zzz.R
@@ -24,8 +24,10 @@ OUT <- 0
     assign("stanc_ctx", V8::v8(), envir = topenv())
   } else assign("stanc_ctx", QuickJSR::JSContext$new(stack_size = 4 * 1024 * 1024), envir = topenv())
   stanc_js <- system.file("stanc.js", package = "StanHeaders", mustWork = TRUE)
-  if (!file.exists(stanc_js)) {
+  test <- try(stanc_ctx$source(stanc_js), silent = TRUE)
+  if (inherits(test, "try-error")) {
     stanc_js <- system.file("exec", "stanc.js", package = "rstan", mustWork = TRUE)
+    stanc_ctx$source(stanc_js)
   }
   stanc_ctx$source(stanc_js)
   assignInMyNamespace("rstan_load_time", value = Sys.time())