diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 0a9123b61bd..11aaeef02bc 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -5189,7 +5189,7 @@ os_spawnve_impl(PyObject *module, int mode, path_t *path, PyObject *argv,
             goto fail_1;
         }
         if (i == 0 && !argvlist[0][0]) {
-            lastarg = i;
+            lastarg = i + 1;
             PyErr_SetString(
                 PyExc_ValueError,
                 "spawnv() arg 2 first element cannot be empty");