diff --git a/src/Data/Text/Internal.hs b/src/Data/Text/Internal.hs
index b88b6068..fec9b5da 100644
--- a/src/Data/Text/Internal.hs
+++ b/src/Data/Text/Internal.hs
@@ -66,6 +66,8 @@ data Text = Text
     {-# UNPACK #-} !Int     -- ^ length in bytes (not in Char!), pointing to an end of UTF-8 sequence
 
 -- | Type synonym for the strict flavour of 'Text'.
+--
+-- @since 2.1.1
 type StrictText = Text
 
 -- | Smart constructor.
diff --git a/src/Data/Text/Internal/Builder.hs b/src/Data/Text/Internal/Builder.hs
index e1116df0..9061af2e 100644
--- a/src/Data/Text/Internal/Builder.hs
+++ b/src/Data/Text/Internal/Builder.hs
@@ -97,6 +97,7 @@ newtype Builder = Builder {
                 -> ST s [S.Text]
    }
 
+-- | @since 2.1.2
 type LazyTextBuilder = Builder
 
 instance Semigroup Builder where
diff --git a/src/Data/Text/Internal/Lazy.hs b/src/Data/Text/Internal/Lazy.hs
index d57d9896..9cf22793 100644
--- a/src/Data/Text/Internal/Lazy.hs
+++ b/src/Data/Text/Internal/Lazy.hs
@@ -56,6 +56,8 @@ data Text = Empty
           -- ^ Chunks must be non-empty, this invariant is not checked.
 
 -- | Type synonym for the lazy flavour of 'Text'.
+--
+-- @since 2.1.1
 type LazyText = Text
 
 -- $invariant