diff --git a/spacy/lemmatizer.py b/spacy/lemmatizer.py
index e51795684..b4323e424 100644
--- a/spacy/lemmatizer.py
+++ b/spacy/lemmatizer.py
@@ -1,7 +1,7 @@
 # coding: utf8
 from __future__ import unicode_literals
 
-from .symbols import POS, NOUN, VERB, ADJ, PUNCT
+from .symbols import POS, NOUN, VERB, ADJ, PUNCT, PROPN
 from .symbols import VerbForm_inf, VerbForm_none, Number_sing, Degree_pos
 
 
@@ -27,11 +27,13 @@ class Lemmatizer(object):
             univ_pos = 'adj'
         elif univ_pos in (PUNCT, 'PUNCT', 'punct'):
             univ_pos = 'punct'
+        elif univ_pos in (PROPN, 'PROPN'):
+            return [string]
         else:
-            return list(set([string.lower()]))
+            return [string.lower()]
         # See Issue #435 for example of where this logic is requied.
         if self.is_base_form(univ_pos, morphology):
-            return list(set([string.lower()]))
+            return [string.lower()]
         lemmas = lemmatize(string, self.index.get(univ_pos, {}),
                            self.exc.get(univ_pos, {}),
                            self.rules.get(univ_pos, []))
@@ -88,6 +90,7 @@ class Lemmatizer(object):
 
 
 def lemmatize(string, index, exceptions, rules):
+    orig = string
     string = string.lower()
     forms = []
     forms.extend(exceptions.get(string, []))
@@ -105,5 +108,5 @@ def lemmatize(string, index, exceptions, rules):
     if not forms:
         forms.extend(oov_forms)
     if not forms:
-        forms.append(string)
+        forms.append(orig)
     return list(set(forms))