diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,10 @@
+Version 1.2.1
+---------------
+* Fix for the `Monus` instance for `Maybe` by Jonathan Knowles
+
 Version 1.2
 ---------------
+* Dropped support for GHC < 8.4
 * Depending on new `commutative-semigroups` package
 * Modified the `instance OverlappingMonoid/Monus Map/IntMap` instances to conform with the class laws
 * Bumped the `vector` dependency upper bounds
diff --git a/Test/TestMonoidSubclasses.hs b/Test/TestMonoidSubclasses.hs
--- a/Test/TestMonoidSubclasses.hs
+++ b/Test/TestMonoidSubclasses.hs
@@ -290,7 +290,9 @@
 monusInstances = [MonusInstance (mempty :: Product Natural),
                   MonusInstance (mempty :: Sum Natural),
                   MonusInstance (mempty :: Dual (Product Natural)),
+                  MonusInstance (mempty :: Maybe ()),
                   MonusInstance (mempty :: Maybe (Product Natural)),
+                  MonusInstance (mempty :: Maybe (Sum Natural)),
                   MonusInstance (mempty :: IntSet),
                   MonusInstance (mempty :: Set String)]
 
diff --git a/monoid-subclasses.cabal b/monoid-subclasses.cabal
--- a/monoid-subclasses.cabal
+++ b/monoid-subclasses.cabal
@@ -1,5 +1,5 @@
 Name:                monoid-subclasses
-Version:             1.2
+Version:             1.2.1
 Cabal-Version:       >= 1.10
 Build-Type:          Simple
 Synopsis:            Subclasses of Monoid
diff --git a/src/Data/Monoid/Monus.hs b/src/Data/Monoid/Monus.hs
--- a/src/Data/Monoid/Monus.hs
+++ b/src/Data/Monoid/Monus.hs
@@ -187,7 +187,11 @@
 -- Maybe instances
 
 instance (Monus a, MonoidNull a) => Monus (Maybe a) where
-   Just a <\> Just b = Just (a <\> b)
+   Just a <\> Just b
+      | null remainder = Nothing
+      | otherwise = Just remainder
+    where
+      remainder = a <\> b
    Nothing <\> _ = Nothing
    x <\> Nothing = x