diff --git a/glib/garray.c b/glib/garray.c
index be482335a..613c6401c 100644
--- a/glib/garray.c
+++ b/glib/garray.c
@@ -1890,6 +1890,7 @@ g_ptr_array_extend_and_steal (GPtrArray  *array_to_extend,
    * to the elements moved from @array to @array_to_extend. */
   pdata = g_steal_pointer (&array->pdata);
   array->len = 0;
+  ((GRealPtrArray *) array)->alloc = 0;
   g_ptr_array_unref (array);
   g_free (pdata);
 }
diff --git a/glib/tests/array-test.c b/glib/tests/array-test.c
index bdd6a2cb9..1da514a3e 100644
--- a/glib/tests/array-test.c
+++ b/glib/tests/array-test.c
@@ -1298,6 +1298,8 @@ pointer_array_extend_and_steal (void)
   g_assert_cmpuint (ptr_array3->len, ==, 0);
   g_assert_null (ptr_array3->pdata);
 
+  g_ptr_array_add (ptr_array2, NULL);
+
   g_ptr_array_free (ptr_array, TRUE);
   g_ptr_array_free (ptr_array3, TRUE);