diff --git a/tabulate/__init__.py b/tabulate/__init__.py
index 12a2950..cf449e6 100644
--- a/tabulate/__init__.py
+++ b/tabulate/__init__.py
@@ -2488,7 +2488,7 @@ def _expand_iterable(original, num_desired, default):
     length `num_desired` completely populated with `default will be returned
     """
     if isinstance(original, Iterable) and not isinstance(original, str):
-        return original + [default] * (num_desired - len(original))
+        return list(original) + [default] * (num_desired - len(original))
     else:
         return [default] * num_desired
 
diff --git a/test/test_internal.py b/test/test_internal.py
index 49ae0ba..b08aea4 100644
--- a/test/test_internal.py
+++ b/test/test_internal.py
@@ -355,3 +355,8 @@ def test__reinsert_separating_lines():
     expected = rows_to_pipe_table_str(with_rows)
 
     assert_equal(expected, rows_to_pipe_table_str(sans_rows))
+
+def test_expand_iterable_accepts_tuple():
+    "Internal: _expand_iterable pads tuples the same way as lists (issue #434)"
+    assert_equal(["top", "bottom"], T._expand_iterable(("top", "bottom"), 2, "top"))
+    assert_equal(["left", "left", "left"], T._expand_iterable(("left",), 3, "left"))
diff --git a/test/test_regression.py b/test/test_regression.py
index 9555676..7f44fde 100644
--- a/test/test_regression.py
+++ b/test/test_regression.py
@@ -598,3 +598,9 @@ def test_github_escape_pipe_character():
     result = tabulate([["foo|bar"]], headers=("spam|eggs",), tablefmt="github")
     expected = "| spam\\|eggs   |\n|:------------|\n| foo\\|bar     |"
     assert_equal(expected, result)
+
+def test_rowalign_tuple():
+    "Regression: rowalign (and other sequence kwargs) accept tuples (issue #434)"
+    result = tabulate([[1, 2], [3, 4]], rowalign=("top", "bottom"))
+    expected = tabulate([[1, 2], [3, 4]], rowalign=["top", "bottom"])
+    assert_equal(expected, result)