diff --git a/tabulate/__init__.py b/tabulate/__init__.py
index 12a2950..11b0650 100644
--- a/tabulate/__init__.py
+++ b/tabulate/__init__.py
@@ -2488,6 +2488,9 @@ 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):
+        # Coerce to list so non-list iterables (e.g. a tuple passed as
+        # `rowalign`/`maxcolwidths`) can be concatenated with the padding list.
+        original = list(original)
         return original + [default] * (num_desired - len(original))
     else:
         return [default] * num_desired
diff --git a/test/test_regression.py b/test/test_regression.py
index 9555676..0ce5df3 100644
--- a/test/test_regression.py
+++ b/test/test_regression.py
@@ -598,3 +598,10 @@ 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 passed as a tuple must not raise (issue #434)."
+    expected = tabulate([[1, 2], [3, 4]], rowalign=["top", "bottom"])
+    result = tabulate([[1, 2], [3, 4]], rowalign=("top", "bottom"))
+    assert_equal(expected, result)