diff --git a/array.c b/array.c
index 1c6c5ab405..115209e136 100644
--- a/array.c
+++ b/array.c
@@ -1108,13 +1108,17 @@ enum ary_take_pos_flags
 static VALUE
 ary_take_first_or_last(int argc, const VALUE *argv, VALUE ary, enum ary_take_pos_flags last)
 {
-    VALUE nv;
     long n;
     long len;
     long offset = 0;
 
-    rb_scan_args(argc, argv, "1", &nv);
-    n = NUM2LONG(nv);
+    argc = rb_check_arity(argc, 0, 1);
+    /* the case optional argument is ommited should be handled in
+     * callers of this function.  if another arity case is added,
+     * this arity check needs to rewrite. */
+    RUBY_ASSERT_WHEN(TRUE, argc == 1);
+
+    n = NUM2LONG(argv[0]);
     len = RARRAY_LEN(ary);
     if (n > len) {
 	n = len;
diff --git a/test/ruby/test_array.rb b/test/ruby/test_array.rb
index aaf3eca58c..4660891e10 100644
--- a/test/ruby/test_array.rb
+++ b/test/ruby/test_array.rb
@@ -146,14 +146,17 @@ class TestArray < Test::Unit::TestCase
     assert_equal(1, x.first)
     assert_equal([1], x.first(1))
     assert_equal([1, 2, 3], x.first(3))
+    assert_raise_with_message(ArgumentError, /0\.\.1/) {x.first(1, 2)}
 
     assert_equal(5, x.last)
     assert_equal([5], x.last(1))
     assert_equal([3, 4, 5], x.last(3))
+    assert_raise_with_message(ArgumentError, /0\.\.1/) {x.last(1, 2)}
 
     assert_equal(1, x.shift)
     assert_equal([2, 3, 4], x.shift(3))
     assert_equal([5], x)
+    assert_raise_with_message(ArgumentError, /0\.\.1/) {x.first(1, 2)}
 
     assert_equal([2, 3, 4, 5], x.unshift(2, 3, 4))
     assert_equal([1, 2, 3, 4, 5], x.unshift(1))
@@ -162,6 +165,7 @@ class TestArray < Test::Unit::TestCase
     assert_equal(5, x.pop)
     assert_equal([3, 4], x.pop(2))
     assert_equal([1, 2], x)
+    assert_raise_with_message(ArgumentError, /0\.\.1/) {x.pop(1, 2)}
 
     assert_equal([1, 2, 3, 4], x.push(3, 4))
     assert_equal([1, 2, 3, 4, 5], x.push(5))
@@ -1585,7 +1589,7 @@ class TestArray < Test::Unit::TestCase
     def o.to_ary
       foo_bar()
     end
-    assert_match(/foo_bar/, assert_raise(NoMethodError) {a.concat(o)}.message)
+    assert_raise_with_message(NoMethodError, /foo_bar/) {a.concat(o)}
   end
 
   def test_to_s