diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,11 @@
 # Changelog for persistent
 
+## 2.13.0.4
+
+* [#1277](https://github.com/yesodweb/persistent/pull/1277)
+    * Corrected the documentation of `addMigration` to match the actual
+      behaviour - this will not change the behaviour of your code.
+
 ## 2.13.0.3
 
 * [#1287](https://github.com/yesodweb/persistent/pull/1287)
@@ -7,6 +13,7 @@
     * Fixes an issue where generating code would refer to the `ModelName` when
       making a reference to another table when the explicit code only refers to
       `ModelNameId`.
+
 
 ## 2.13.0.2
 
diff --git a/Database/Persist/Sql/Migration.hs b/Database/Persist/Sql/Migration.hs
--- a/Database/Persist/Sql/Migration.hs
+++ b/Database/Persist/Sql/Migration.hs
@@ -22,20 +22,20 @@
 import Control.Exception (throwIO)
 import Control.Monad (liftM, unless)
 import Control.Monad.IO.Unlift
-import Control.Monad.Trans.Class (MonadTrans (..))
-import Control.Monad.Trans.Reader (ReaderT (..), ask)
+import Control.Monad.Trans.Class (MonadTrans(..))
+import Control.Monad.Trans.Reader (ReaderT(..), ask)
 import Control.Monad.Trans.Writer
-import Data.Text (Text, unpack, snoc, isPrefixOf, pack)
+import Data.Text (Text, isPrefixOf, pack, snoc, unpack)
 import qualified Data.Text.IO
+import GHC.Stack
 import System.IO
 import System.IO.Silently (hSilence)
-import GHC.Stack
 
+import Database.Persist.Sql.Orphan.PersistStore ()
+import Database.Persist.Sql.Raw
 import Database.Persist.Sql.Types
 import Database.Persist.Sql.Types.Internal
-import Database.Persist.Sql.Raw
 import Database.Persist.Types
-import Database.Persist.Sql.Orphan.PersistStore()
 
 allSql :: CautiousMigration -> [Sql]
 allSql = map snd
@@ -195,12 +195,14 @@
 -- @since 2.9.2
 addMigration
     :: Bool
-    -- ^ Is the migration safe to run? (eg a non-destructive and idempotent
-    -- update on the schema)
+    -- ^ Is the migration unsafe to run? (eg a destructive or non-idempotent
+    -- update on the schema). If 'True', the migration is *unsafe*, and will
+    -- need to be run manually later. If 'False', the migration is *safe*, and
+    -- can be run any number of times.
     -> Sql
     -- ^ A 'Text' value representing the command to run on the database.
     -> Migration
-addMigration isSafe sql = lift (tell [(isSafe, sql)])
+addMigration isUnsafe sql = lift (tell [(isUnsafe, sql)])
 
 -- | Add a 'CautiousMigration' (aka a @[('Bool', 'Text')]@) to the
 -- migration plan.
diff --git a/Database/Persist/Sql/Types.hs b/Database/Persist/Sql/Types.hs
--- a/Database/Persist/Sql/Types.hs
+++ b/Database/Persist/Sql/Types.hs
@@ -63,7 +63,10 @@
 
 type Sql = Text
 
--- Bool indicates if the Sql is safe
+-- | A list of SQL operations, marked with a safety flag. If the 'Bool' is
+-- 'True', then the operation is *unsafe* - it might be destructive, or
+-- otherwise not idempotent. If the 'Bool' is 'False', then the operation
+-- is *safe*, and can be run repeatedly without issues.
 type CautiousMigration = [(Bool, Sql)]
 
 -- | A 'Migration' is a four level monad stack consisting of:
diff --git a/persistent.cabal b/persistent.cabal
--- a/persistent.cabal
+++ b/persistent.cabal
@@ -1,5 +1,5 @@
 name:            persistent
-version:         2.13.0.3
+version:         2.13.0.4
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>