diff --git a/Python/pathconfig.c b/Python/pathconfig.c
index f96f015..41fc9e2 100644
--- a/Python/pathconfig.c
+++ b/Python/pathconfig.c
@@ -330,7 +330,7 @@
 #endif
 
     if (path_config.isolated != -1) {
-        config->isolated = path_config.isolated;
+        config->preconfig.isolated = path_config.isolated;
     }
     if (path_config.site_import != -1) {
         config->site_import = path_config.site_import;