diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+# 0.4.2.1
+
+* Fixed [lens bug #799](https://github.com/ekmett/lens/issues/799) (`makeFields` instances violate coverage condition).
+
 # 0.4.2
 
 * We now depend on `th-abstraction` (like `lens` itself).
@@ -21,7 +25,7 @@
 
 # 0.4.0.1
 
-* Ported a lens commit that (probably) makes lens generation deterministic. See [this issue](https://github.com/aelve/microlens/issues/83).
+* Ported a lens commit that (probably) makes lens generation deterministic. See [issue #83](https://github.com/aelve/microlens/issues/83).
 
 # 0.4.0.0
 
diff --git a/microlens-th.cabal b/microlens-th.cabal
--- a/microlens-th.cabal
+++ b/microlens-th.cabal
@@ -1,5 +1,5 @@
 name:                microlens-th
-version:             0.4.2
+version:             0.4.2.1
 synopsis:            Automatic generation of record lenses for microlens
 description:
   This package lets you automatically generate lenses for data types; code was extracted from the lens package, and therefore generated lenses are fully compatible with ones generated by lens (and can be used both from lens and microlens).
@@ -52,6 +52,7 @@
 test-suite templates
   type: exitcode-stdio-1.0
   main-is: templates.hs
+  other-modules: T799
   ghc-options: -Wall -threaded
   hs-source-dirs: test
 
diff --git a/src/Lens/Micro/TH.hs b/src/Lens/Micro/TH.hs
--- a/src/Lens/Micro/TH.hs
+++ b/src/Lens/Micro/TH.hs
@@ -1138,9 +1138,20 @@
 
   containsTypeFamilies = go <=< D.resolveTypeSynonyms
     where
-    go (ConT nm) = (\i -> case i of FamilyI{} -> True; _ -> False)
+    go (ConT nm) = (\i -> case i of FamilyI d _ -> isTypeFamily d; _ -> False)
                    <$> reify nm
     go ty = or <$> traverse go (children ty)
+
+#if MIN_VERSION_template_haskell(2,11,0)
+  isTypeFamily OpenTypeFamilyD{}       = True
+  isTypeFamily ClosedTypeFamilyD{}     = True
+#elif MIN_VERSION_template_haskell(2,9,0)
+  isTypeFamily (FamilyD TypeFam _ _ _) = True
+  isTypeFamily ClosedTypeFamilyD{}     = True
+#else
+  isTypeFamily (FamilyD TypeFam _ _ _) = True
+#endif
+  isTypeFamily _ = False
 
   pickInstanceDec hasFamilies
     | hasFamilies = do
diff --git a/test/T799.hs b/test/T799.hs
new file mode 100644
--- /dev/null
+++ b/test/T799.hs
@@ -0,0 +1,24 @@
+{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE FunctionalDependencies #-}
+{-# LANGUAGE MultiParamTypeClasses #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeFamilies #-}
+-- | Test 'makeFields' on a field whose type has a data family. Unlike for
+-- type families, for data families we do not generate type equality
+-- constraints, as they are not needed to avoid the issue in #754.
+--
+-- This tests that the fix for #799 is valid by putting this in a module in
+-- which UndecidableInstances is not enabled.
+module T799 where
+
+import Lens.Micro
+import Lens.Micro.TH
+
+data family DF a
+newtype instance DF Int = FooInt Int
+
+data Bar = Bar { _barFoo :: DF Int }
+makeFields ''Bar
+
+checkBarFoo :: Lens' Bar (DF Int)
+checkBarFoo = foo
diff --git a/test/templates.hs b/test/templates.hs
--- a/test/templates.hs
+++ b/test/templates.hs
@@ -26,6 +26,7 @@
 
 import Lens.Micro
 import Lens.Micro.TH
+import T799 ()
 
 data Bar a b c = Bar { _baz :: (a, b) }
 makeLenses ''Bar