diff --git a/pymongo/collection.py b/pymongo/collection.py
index affdf93d5..ba8e3f1db 100644
--- a/pymongo/collection.py
+++ b/pymongo/collection.py
@@ -1052,7 +1052,7 @@ class Collection(common.BaseObject):
                                     read_preference=ReadPreference.PRIMARY,
                                     indexes=[index])
         except OperationFailure, exc:
-            if exc.code in (59, None):
+            if exc.code in common.COMMAND_NOT_FOUND_CODES:
                 index["ns"] = self.__full_name
                 self.__database.system.indexes.insert(index, manipulate=False,
                                                       check_keys=False,
diff --git a/pymongo/common.py b/pymongo/common.py
index f246339c7..60d618d16 100644
--- a/pymongo/common.py
+++ b/pymongo/common.py
@@ -47,6 +47,14 @@ MAX_WRITE_BATCH_SIZE = 1000
 MIN_SUPPORTED_WIRE_VERSION = 0
 MAX_SUPPORTED_WIRE_VERSION = 2
 
+# mongod/s 2.6 and above return code 59 when a
+# command doesn't exist. mongod versions previous
+# to 2.6 and mongos 2.4.x return no error code
+# when a command does exist. mongos versions previous
+# to 2.4.0 return code 13390 when a command does not
+# exist.
+COMMAND_NOT_FOUND_CODES = (59, 13390, None)
+
 
 def raise_config_error(key, dummy):
     """Raise ConfigurationError with the given key name."""
diff --git a/pymongo/database.py b/pymongo/database.py
index f565b7260..49e0a7eb3 100644
--- a/pymongo/database.py
+++ b/pymongo/database.py
@@ -779,11 +779,8 @@ class Database(common.BaseObject):
                                  read_preference=ReadPreference.PRIMARY)
         except OperationFailure, exc:
             # MongoDB >= 2.5.3 requires the use of commands to manage
-            # users. "No such command" error didn't return an error
-            # code (59) before MongoDB 2.4.7 so we assume that an error
-            # code of None means the userInfo command doesn't exist and
-            # we should fall back to the legacy add user code.
-            if exc.code in (59, None):
+            # users.
+            if exc.code in common.COMMAND_NOT_FOUND_CODES:
                 self._legacy_add_user(name, password, read_only, **kwargs)
                 return
             raise