diff --git a/.travis.yml b/.travis.yml
index 37b56e6a..9dd069c7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,7 +7,6 @@ language: python
 
 matrix:
   include:
-    - python: 2.7
     - python: 3.6
 
 env:
diff --git a/setup.py b/setup.py
index 7bf32f88..dd1a6c42 100755
--- a/setup.py
+++ b/setup.py
@@ -17,6 +17,7 @@
       license='BSD',
       keywords='streams',
       packages=packages + tests,
+      python_requires='>=3.5',
       long_description=(open('README.rst').read() if exists('README.rst')
                         else ''),
       install_requires=list(open('requirements.txt').read().strip().split('\n')),
diff --git a/streamz/core.py b/streamz/core.py
index e22eec70..305f62d4 100644
--- a/streamz/core.py
+++ b/streamz/core.py
@@ -1035,6 +1035,20 @@ class unique(Stream):
     parameter.  For example setting ``history=1`` avoids sending through
     elements when one is repeated right after the other.
 
+    Parameters
+    ----------
+    history : int or None, optional
+        number of stored unique values to check against
+    key : function, optional
+        Function which returns a representation of the incoming data.
+        For example ``key=lambda x: x['a']`` could be used to allow only
+        pieces of data with unique ``'a'`` values to pass through.
+    hashable : bool, optional
+        If True then data is assumed to be hashable, else it is not. This is
+        used for determining how to cache the history, if hashable then
+        either dicts or LRU caches are used, otherwise a deque is used.
+        Defaults to True.
+
     Examples
     --------
     >>> source = Stream()
@@ -1046,20 +1060,36 @@ class unique(Stream):
     1
     3
     """
-    def __init__(self, upstream, history=None, key=identity, **kwargs):
-        self.seen = dict()
+    def __init__(self, upstream, maxsize=None, key=identity, hashable=True,
+                 **kwargs):
         self.key = key
-        if history:
-            from zict import LRU
-            self.seen = LRU(history, self.seen)
+        self.maxsize = maxsize
+        if hashable:
+            self.seen = dict()
+            if self.maxsize:
+                from zict import LRU
+                self.seen = LRU(self.maxsize, self.seen)
+        else:
+            self.seen = []
 
         Stream.__init__(self, upstream, **kwargs)
 
     def update(self, x, who=None):
         y = self.key(x)
-        if y not in self.seen:
-            self.seen[y] = 1
-            return self._emit(x)
+        emit = True
+        if isinstance(self.seen, list):
+            if y in self.seen:
+                self.seen.remove(y)
+                emit = False
+            self.seen.insert(0, y)
+            if self.maxsize:
+                del self.seen[self.maxsize:]
+            if emit:
+                return self._emit(x)
+        else:
+            if self.seen.get(y, '~~not_seen~~') == '~~not_seen~~':
+                self.seen[y] = 1
+                return self._emit(x)
 
 
 @Stream.register_api()
diff --git a/streamz/tests/test_core.py b/streamz/tests/test_core.py
index 3845de60..34c69af6 100644
--- a/streamz/tests/test_core.py
+++ b/streamz/tests/test_core.py
@@ -487,7 +487,7 @@ def test_unique():
 
 def test_unique_key():
     source = Stream()
-    L = source.unique(key=lambda x: x % 2, history=1).sink_to_list()
+    L = source.unique(key=lambda x: x % 2, maxsize=1).sink_to_list()
 
     source.emit(1)
     source.emit(2)
@@ -500,8 +500,10 @@ def test_unique_key():
 
 def test_unique_history():
     source = Stream()
-    s = source.unique(history=2)
+    s = source.unique(maxsize=2)
+    s2 = source.unique(maxsize=2, hashable=False)
     L = s.sink_to_list()
+    L2 = s2.sink_to_list()
 
     source.emit(1)
     source.emit(2)
@@ -511,15 +513,56 @@ def test_unique_history():
     source.emit(2)
 
     assert L == [1, 2]
+    assert L == L2
 
     source.emit(3)
     source.emit(2)
 
     assert L == [1, 2, 3]
+    assert L == L2
 
     source.emit(1)
 
     assert L == [1, 2, 3, 1]
+    assert L == L2
+
+    # update 2 position
+    source.emit(2)
+    # knock out 1
+    source.emit(3)
+    # update 2 position
+    source.emit(2)
+
+    assert L == [1, 2, 3, 1, 3]
+    assert L == L2
+
+
+def test_unique_history_dict():
+    source = Stream()
+    s = source.unique(maxsize=2, hashable=False)
+    L = s.sink_to_list()
+
+    a = {'hi': 'world'}
+    b = {'hi': 'bar'}
+    c = {'foo': 'bar'}
+
+    source.emit(a)
+    source.emit(b)
+    source.emit(a)
+    source.emit(b)
+    source.emit(a)
+    source.emit(b)
+
+    assert L == [a, b]
+
+    source.emit(c)
+    source.emit(b)
+
+    assert L == [a, b, c]
+
+    source.emit(a)
+
+    assert L == [a, b, c, a]
 
 
 def test_union():