diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
index 55eade1c8307ea..640e770f8ae747 100644
--- a/Modules/_ctypes/_ctypes.c
+++ b/Modules/_ctypes/_ctypes.c
@@ -2367,7 +2367,10 @@ PyCSimpleType_init(PyObject *self, PyObject *args, PyObject *kwds)
         stginfo->ffi_type_pointer = *fmt->pffi_type;
     }
     else {
-        const size_t els_size = sizeof(fmt->pffi_type->elements);
+        /* From primitive types - only complex types have the elements
+           struct field as non-NULL (two element array). */
+        assert(fmt->pffi_type->type == FFI_TYPE_COMPLEX);
+        const size_t els_size = 2 * sizeof(ffi_type *);
         stginfo->ffi_type_pointer.size = fmt->pffi_type->size;
         stginfo->ffi_type_pointer.alignment = fmt->pffi_type->alignment;
         stginfo->ffi_type_pointer.type = fmt->pffi_type->type;