diff --git a/dtool/src/dtoolutil/executionEnvironment.cxx b/dtool/src/dtoolutil/executionEnvironment.cxx
index 8236e68276..03dd22146d 100644
--- a/dtool/src/dtoolutil/executionEnvironment.cxx
+++ b/dtool/src/dtoolutil/executionEnvironment.cxx
@@ -214,7 +214,7 @@ ns_get_environment_variable(const string &var) const {
   } else if (var == "MAIN_DIR") {
 #ifdef HAVE_PYTHON
     // If we're running from Python code, read out sys.argv.
-    if (PyObject* obj = PySys_GetObject((char*) "argv")) {
+    if (Py_IsInitialized() && PyObject* obj = PySys_GetObject((char*) "argv")) {
       Filename main_dir (PyString_AsString(PyList_GetItem(obj, 0)));
       if (main_dir.empty()) {
         // We must be running in the Python interpreter directly, so return the CWD.