diff --git a/asn1crypto/cms.py b/asn1crypto/cms.py
index c395b22..b104c99 100644
--- a/asn1crypto/cms.py
+++ b/asn1crypto/cms.py
@@ -729,6 +729,12 @@ class RecipientKeyIdentifier(Sequence):
         ('other', OtherKeyAttribute, {'optional': True}),
     ]
 
+    def _setup(self):
+        super(RecipientKeyIdentifier, self)._setup()
+        # This creates a backwards compatible shim for an
+        # incorrect format field name that was in old versions
+        self._field_map['subjectKeyIdentifier'] = self._field_map['subject_key_identifier']
+
 
 class KeyAgreementRecipientIdentifier(Choice):
     _alternatives = [
@@ -929,21 +935,20 @@ def decompressed(self):
         return self._decompressed
 
 
-class RecipientKeyIdentifier(Sequence):
-    _fields = [
-        ('subjectKeyIdentifier', OctetString),
-        ('date', GeneralizedTime, {'optional': True}),
-        ('other', OtherKeyAttribute, {'optional': True}),
-    ]
-
-
 class SMIMEEncryptionKeyPreference(Choice):
     _alternatives = [
         ('issuer_and_serial_number', IssuerAndSerialNumber, {'implicit': 0}),
-        ('recipientKeyId', RecipientKeyIdentifier, {'implicit': 1}),
-        ('subjectAltKeyIdentifier', PublicKeyInfo, {'implicit': 2}),
+        ('recipient_key_id', RecipientKeyIdentifier, {'implicit': 1}),
+        ('subject_alt_key_identifier', PublicKeyInfo, {'implicit': 2}),
     ]
 
+    def _setup(self):
+        super(SMIMEEncryptionKeyPreference, self)._setup()
+        # This creates backwards compatible shims for two
+        # incorrect format alternative names that were in old versions
+        self._name_map['recipientKeyId'] = self._name_map['recipient_key_id']
+        self._name_map['subjectAltKeyIdentifier'] = self._name_map['subject_alt_key_identifier']
+
 
 class SMIMEEncryptionKeyPreferences(SetOf):
     _child_spec = SMIMEEncryptionKeyPreference
diff --git a/asn1crypto/core.py b/asn1crypto/core.py
index 2edd4f3..428ef0e 100644
--- a/asn1crypto/core.py
+++ b/asn1crypto/core.py
@@ -3429,6 +3429,17 @@ def __init__(self, value=None, default=None, **kwargs):
                         self.__setitem__(key, value[key])
                         unused_keys.remove(key)
 
+                # This handles the situation where there is field name
+                # mapping going on due to a field be renamed. Normally
+                # the keys are checked against the primary field list.
+                # If there are still keys left over, check to see if they
+                # are mapped via checking the _field_map.
+                if len(unused_keys):
+                    for key in list(unused_keys):
+                        if key in self._field_map:
+                            self.__setitem__(key, value[key])
+                            unused_keys.remove(key)
+
                 if len(unused_keys):
                     raise ValueError(unwrap(
                         '''
diff --git a/tests/test_cms.py b/tests/test_cms.py
index 8f9b1e6..2698282 100644
--- a/tests/test_cms.py
+++ b/tests/test_cms.py
@@ -1001,3 +1001,41 @@ def test_create_role_syntax(self):
             ]),
             rs.native
         )
+
+    def test_backwards_compat_field_name(self):
+        new_version = cms.RecipientKeyIdentifier({'subject_key_identifier': b'\x08\x09\x10'})
+        old_version = cms.RecipientKeyIdentifier({'subjectKeyIdentifier': b'\x08\x09\x10'})
+        self.assertEqual(
+            new_version.dump(True),
+            old_version.dump(True),
+        )
+        self.assertEqual(
+            new_version.native,
+            old_version.native,
+        )
+
+    def test_backwards_compat_choice_names(self):
+        rki = cms.RecipientKeyIdentifier({'subject_key_identifier': b'\x08\x09\x10'})
+        new_sekp = cms.SMIMEEncryptionKeyPreference({'recipient_key_id': rki})
+        old_sekp = cms.SMIMEEncryptionKeyPreference({'recipientKeyId': rki})
+
+        self.assertEqual(
+            new_sekp.dump(True),
+            old_sekp.dump(True),
+        )
+        self.assertEqual(
+            new_sekp.native,
+            old_sekp.native,
+        )
+        self.assertEqual(
+            new_sekp.chosen.untag().dump(True),
+            rki.dump(True),
+        )
+        self.assertEqual(
+            'recipient_key_id',
+            new_sekp.name,
+        )
+        self.assertEqual(
+            'recipient_key_id',
+            old_sekp.name,
+        )