diff --git a/django/newforms/widgets.py b/django/newforms/widgets.py
index 18bba31897..58d8ab1322 100644
--- a/django/newforms/widgets.py
+++ b/django/newforms/widgets.py
@@ -24,7 +24,10 @@ class Widget(object):
     is_hidden = False          # Determines whether this corresponds to an <input type="hidden">.
 
     def __init__(self, attrs=None):
-        self.attrs = attrs or {}
+        if attrs is not None:
+            self.attrs = attrs.copy()
+        else:
+            self.attrs = {}
 
     def render(self, name, value, attrs=None):
         """
diff --git a/tests/regressiontests/forms/regressions.py b/tests/regressiontests/forms/regressions.py
new file mode 100644
index 0000000000..dc5232a8f0
--- /dev/null
+++ b/tests/regressiontests/forms/regressions.py
@@ -0,0 +1,13 @@
+# -*- coding: utf-8 -*-
+# Tests to prevent against recurrences of earlier bugs.
+
+regression_tests = r"""
+It should be possible to re-use attribute dictionaries (#3810)
+>>> from django.newforms import *
+>>> extra_attrs = {'class': 'special'}
+>>> class TestForm(Form):
+...     f1 = CharField(max_length=10, widget=TextInput(attrs=extra_attrs))
+...     f2 = CharField(widget=TextInput(attrs=extra_attrs))
+>>> TestForm(auto_id=False).as_p()
+u'<p>F1: <input type="text" class="special" name="f1" maxlength="10" /></p>\n<p>F2: <input type="text" class="special" name="f2" /></p>'
+"""
diff --git a/tests/regressiontests/forms/tests.py b/tests/regressiontests/forms/tests.py
index 0bd87c1751..8ecc9f0205 100644
--- a/tests/regressiontests/forms/tests.py
+++ b/tests/regressiontests/forms/tests.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 from localflavor import localflavor_tests
+from regressions import regression_tests
 
 form_tests = r"""
 >>> from django.newforms import *
@@ -3297,6 +3298,7 @@ u'foo'
 __test__ = {
     'form_tests': form_tests,
     'localflavor': localflavor_tests,
+    'regressions': regression_tests,
 }
 
 if __name__ == "__main__":