diff --git a/message-index/messages/GHC-59692/index.md b/message-index/messages/GHC-59692/index.md
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+---
+title: Duplicate Instances
+summary: Multiple instances defined for the same type class and type.
+severity: error
+introduced: 9.6.1
+---
+
+For type class coherence, at most one instance may be defined for each type for the same type class.
+
+Identical instances should simply be removed.
+If multiple instances for the same type are required, circumventing this restriction is possible by introducing a `newtype` wrapper.
diff --git a/message-index/messages/GHC-59692/multipleInstances/after/MultipleInstances.hs b/message-index/messages/GHC-59692/multipleInstances/after/MultipleInstances.hs
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+++ b/message-index/messages/GHC-59692/multipleInstances/after/MultipleInstances.hs
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+module MultipleInstances where
+
+newtype Sum = Sum { getSum :: Int }
+
+instance Semigroup Sum where
+    (<>) x y = Sum (getSum x + getSum y)
+
+newtype Product = Product { getProduct :: Int }
+
+instance Semigroup Product where
+    (<>) x y = Product (getProduct x * getProduct y)
diff --git a/message-index/messages/GHC-59692/multipleInstances/before/MultipleInstances.hs b/message-index/messages/GHC-59692/multipleInstances/before/MultipleInstances.hs
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+module MultipleInstances where
+
+instance Semigroup Int where
+    (<>) = (+)
+
+instance Semigroup Int where
+    (<>) = (*)
diff --git a/message-index/messages/GHC-59692/multipleInstances/index.md b/message-index/messages/GHC-59692/multipleInstances/index.md
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+---
+title: Multiple Instances for Semigroup Int
+---
+
+Haskell does not allow to give more than one definition of `Semigroup Int`, even though we might want to provide both an instance for the semigroup given by multiplication and the semigroup given by addition.
+If we require both instances, then we should define two `newtype` wrappers for `Int`.