diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -7,6 +7,9 @@
 
 # Changelog
 
+* 3.0.0.1
+  - Fixed GHC 8.2.2 "Type indexes must match class instance head" compile error.
+
 * 3.0.0.0
   - Renamed `SelectWith` to `MakeFrom`, split `ChooseBtween` to `ChooseBoth` and `ChooseFrom`.
   - Removed hard to remember operators ``>&&>` `*&&*` `+||+` `>||>`
diff --git a/data-diverse-lens.cabal b/data-diverse-lens.cabal
--- a/data-diverse-lens.cabal
+++ b/data-diverse-lens.cabal
@@ -1,5 +1,5 @@
 name:                data-diverse-lens
-version:             3.0.0.0
+version:             3.0.0.1
 synopsis:            Isos & Lens for Data.Diverse.Many and Prisms for Data.Diverse.Which
 description:         Isos & Lens for Data.Diverse.Many and Prisms for Data.Diverse.Which
                      Refer to [ManySpec.hs](https://github.com/louispan/data-diverse-lens/blob/master/test/Data/Diverse/Lens/ManySpec.hs) and [WhichSpec.hs](https://github.com/louispan/data-diverse-lens/blob/master/test/Data/Diverse/Lens/WhichSpec.hs) for example usages.
diff --git a/src/Data/Diverse/Lens/Many.hs b/src/Data/Diverse/Lens/Many.hs
--- a/src/Data/Diverse/Lens/Many.hs
+++ b/src/Data/Diverse/Lens/Many.hs
@@ -88,7 +88,7 @@
     item :: Lens s (Replaced a b s) a b
 
 instance (UniqueMember x xs) => HasItem x (Many xs) where
-    type Replaced a b (Many xs) = Many (Replace a b xs)
+    type Replaced x b (Many xs) = Many (Replace x b xs)
     item = lens grab (replace @x)
 
 -- | 'grabL' ('view' 'itemL') and 'replaceL' ('set' 'itemL') in 'Lens'' form.
@@ -124,7 +124,7 @@
     itemL :: Lens s (ReplacedL l a b s) a b
 
 instance (UniqueLabelMember l xs, x ~ KindAtLabel l xs) => HasItemL l x (Many xs) where
-    type ReplacedL l _ b (Many xs) = Many (Replace (KindAtLabel l xs) b xs)
+    type ReplacedL l x b (Many xs) = Many (Replace (KindAtLabel l xs) b xs)
     itemL = lens (grabL @l) (replaceL @l)
 
 -- | Variation of 'itemL'' that automatically tags and untags a Tagged field.
@@ -167,7 +167,7 @@
 
 instance (MemberAt n x xs)
   => HasItemN n x (Many xs) where
-    type ReplacedN n a b (Many xs) = Many (ReplaceIndex n a b xs)
+    type ReplacedN n x b (Many xs) = Many (ReplaceIndex n x b xs)
     itemN = lens (grabN @n) (replaceN @n)
 
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