diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
-# 0.1.0.0
+# 0.2.0 (2021-10-24)
+
+* Make `unSInt` part of a unidirectional pattern synonym.
+  * Migration: replace record updates of `unSInt` with `SI#`.
+
+# 0.1.0.0 (2021-09-07)
 
 Initial version.
diff --git a/README.md b/README.md
new file mode 100644
--- /dev/null
+++ b/README.md
@@ -0,0 +1,11 @@
+# sint
+
+A singleton type for `Nat` represented as `Int`.
+
+This package implements a type `SInt` that links a runtime `Int` with a
+type-level `Nat`, along with some arithmetic and reflection capabilities.
+
+This is useful when mixing type-level `Nat`s with GHC array primitives that
+expect `Int`s as sizes and indices.
+
+See the module intro of `Data.SInt` for more details.
diff --git a/sint.cabal b/sint.cabal
--- a/sint.cabal
+++ b/sint.cabal
@@ -1,14 +1,12 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.33.0.
+-- This file has been generated from package.yaml by hpack version 0.34.4.
 --
 -- see: https://github.com/sol/hpack
---
--- hash: ceb4a5946c62e4214f0149eb3292465831eb7758e6dd5435ab1fb3d771813708
 
 name:           sint
-version:        0.1.0.0
-synopsis:       A singleton type for `Nat` represented as `Int`.
+version:        0.2.0
+synopsis:       Nat singletons represented by Int
 description:    This package implements a type `SInt` that links a runtime `Int` with a
                 type-level `Nat`, along with some arithmetic and reflection capabilities.
                 .
@@ -27,6 +25,7 @@
 build-type:     Simple
 extra-source-files:
     CHANGELOG.md
+    README.md
 
 source-repository head
   type: git
@@ -36,28 +35,24 @@
 library
   exposed-modules:
       Data.SInt
-  other-modules:
-      Paths_sint
   hs-source-dirs:
       src
   build-depends:
       base >=4.12 && <4.16
-    , portray >=0.1 && <0.2
-    , portray-diff >=0.1 && <0.2
+    , portray >=0.1 && <0.3
+    , portray-diff ==0.1.*
   default-language: Haskell2010
 
 test-suite SInt-test
   type: exitcode-stdio-1.0
   main-is: Main.hs
-  other-modules:
-      Paths_sint
   hs-source-dirs:
       test
   build-depends:
       QuickCheck
     , base >=4.12 && <4.16
-    , portray >=0.1 && <0.2
-    , portray-diff >=0.1 && <0.2
+    , portray >=0.1 && <0.3
+    , portray-diff ==0.1.*
     , sint
     , test-framework
     , test-framework-quickcheck2
diff --git a/src/Data/SInt.hs b/src/Data/SInt.hs
--- a/src/Data/SInt.hs
+++ b/src/Data/SInt.hs
@@ -57,7 +57,7 @@
 #include "MachDeps.h"
 
 module Data.SInt
-         ( SInt(SI#, unSInt), trySIntVal, sintVal, reifySInt, withSInt
+         ( SInt(SI#, SI, unSInt), trySIntVal, sintVal, reifySInt, withSInt
          , addSInt, subSInt, subSIntLE, subSIntL, mulSInt, divSIntL, divSIntR
          , staticSIntVal
            -- * Internal
@@ -96,8 +96,16 @@
 -- construct 'SInt's, and treat this constructor equivalently to
 -- 'unsafeCoerce'.
 pattern SI# :: Int -> SInt n
-pattern SI# {unSInt} = MkSInt unSInt
+pattern SI# x = MkSInt x
 {-# COMPLETE SI# #-}
+
+-- | A unidirectional pattern for safely deconstructing 'SInt's.
+--
+-- This lets us export 'unSInt' as if it were a field selector, without making
+-- it legal to use in record updates (because this pattern is unidirectional).
+pattern SI :: Int -> SInt n
+pattern SI {unSInt} <- MkSInt unSInt
+{-# COMPLETE SI #-}
 
 -- | Use an 'Int' as an existentially-quantified 'SInt'.
 withSInt :: HasCallStack => Int -> (forall n. SInt n -> r) -> r