diff --git a/toolz/itertoolz.py b/toolz/itertoolz.py
index 354ecf25..c5e37343 100644
--- a/toolz/itertoolz.py
+++ b/toolz/itertoolz.py
@@ -319,6 +319,8 @@ def take(n, seq):
         drop
         tail
     """
+    if n < 0:
+        raise ValueError('take: n must be a non-negative integer, got %r' % (n,))
     return itertools.islice(seq, n)
 
 
@@ -348,6 +350,8 @@ def drop(n, seq):
         take
         tail
     """
+    if n < 0:
+        raise ValueError('drop: n must be a non-negative integer, got %r' % (n,))
     return itertools.islice(seq, n, None)
 
 
diff --git a/toolz/tests/test_itertoolz.py b/toolz/tests/test_itertoolz.py
index c8640917..f756d89f 100644
--- a/toolz/tests/test_itertoolz.py
+++ b/toolz/tests/test_itertoolz.py
@@ -185,6 +185,15 @@ def test_take():
     assert list(take(2, (3, 2, 1))) == list((3, 2))
 
 
+def test_take_negative_n():
+    try:
+        list(take(-1, [1, 2, 3]))
+        assert False, 'expected ValueError'
+    except ValueError as e:
+        assert 'non-negative' in str(e)
+    assert list(take(0, [1, 2, 3])) == []   # n == 0 boundary still returns, not rejected
+
+
 def test_tail():
     assert list(tail(3, 'ABCDE')) == list('CDE')
     assert list(tail(3, iter('ABCDE'))) == list('CDE')
@@ -196,6 +205,15 @@ def test_drop():
     assert list(drop(1, (3, 2, 1))) == list((2, 1))
 
 
+def test_drop_negative_n():
+    try:
+        list(drop(-1, [1, 2, 3]))
+        assert False, 'expected ValueError'
+    except ValueError as e:
+        assert 'non-negative' in str(e)
+    assert list(drop(0, [1, 2, 3])) == [1, 2, 3]
+
+
 def test_take_nth():
     assert list(take_nth(2, 'ABCDE')) == list('ACE')