diff --git a/Python/sysmodule.c b/Python/sysmodule.c
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1721,7 +1721,7 @@
 {
     wchar_t *argv0;
     wchar_t *p = NULL;
-    Py_ssize_t n = 0;
+    Py_ssize_t n;
     PyObject *a;
     PyObject *path;
 #ifdef HAVE_READLINK
@@ -1739,7 +1739,13 @@
     if (path == NULL)
         return;
 
-    argv0 = argv[0];
+    if (argc > 0) {
+        argv0 = argv[0];
+        n = wcslen(argv0);
+    } else {
+        argv0 = NULL;
+        n = 0;
+    }
 
 #ifdef HAVE_READLINK
     if (_HAVE_SCRIPT_ARGUMENT(argc, argv))