diff --git a/compiler/deSugar/DsForeign.hs b/compiler/deSugar/DsForeign.hs
--- a/compiler/deSugar/DsForeign.hs
+++ b/compiler/deSugar/DsForeign.hs
@@ -682,7 +682,10 @@
    -- See Note [Tracking foreign exports] in rts/ForeignExports.c
    vcat
     [ text "static struct ForeignExportsList" <+> list_symbol <+> equals
-         <+> braces (text ".exports = " <+> export_list) <> semi
+         <+> braces (
+           text ".exports = " <+> export_list <> comma <+>
+           text ".n_entries = " <+> ppr (length hs_fns))
+         <> semi
     , text "static void " <> ctor_symbol <> text "(void)"
          <+> text " __attribute__((constructor));"
     , text "static void " <> ctor_symbol <> text "()"
diff --git a/compiler/typecheck/TcTyClsDecls.hs b/compiler/typecheck/TcTyClsDecls.hs
--- a/compiler/typecheck/TcTyClsDecls.hs
+++ b/compiler/typecheck/TcTyClsDecls.hs
@@ -2747,6 +2747,9 @@
                                 -- GHC.Rename.Source
                                 tcInferApps typeLevelMode lhs_fun fun_ty hs_pats
 
+       -- Hack alert: see Note [tcFamTyPats: zonking the result kind]
+       ; res_kind <- zonkTcType res_kind
+
        ; traceTc "End tcFamTyPats }" $
          vcat [ ppr fam_tc, text "res_kind:" <+> ppr res_kind ]
 
@@ -2755,6 +2758,33 @@
     fam_name  = tyConName fam_tc
     fam_arity = tyConArity fam_tc
     lhs_fun   = noLoc (HsTyVar noExtField NotPromoted (noLoc fam_name))
+
+{- Note [tcFamTyPats: zonking the result kind]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider (#19250)
+    F :: forall k. k -> k
+    type instance F (x :: Constraint) = ()
+
+The tricky point is this:
+  is that () an empty type tuple (() :: Type), or
+  an empty constraint tuple (() :: Constraint)?
+We work this out in a hacky way, by looking at the expected kind:
+see Note [Inferring tuple kinds].
+
+In this case, we kind-check the RHS using the kind gotten from the LHS:
+see the call to tcCheckLHsType in tcTyFamInstEqnGuts in GHC.Tc.Tycl.
+
+But we want the kind from the LHS to be /zonked/, so that when
+kind-checking the RHS (tcCheckLHsType) we can "see" what we learned
+from kind-checking the LHS (tcFamTyPats).  In our example above, the
+type of the LHS is just `kappa` (by instantiating the forall k), but
+then we learn (from x::Constraint) that kappa ~ Constraint.  We want
+that info when kind-checking the RHS.
+
+Easy solution: just zonk that return kind.  Of course this won't help
+if there is lots of type-family reduction to do, but it works fine in
+common cases.
+-}
 
 unravelFamInstPats :: TcType -> [TcType]
 -- Decompose fam_app to get the argument patterns
diff --git a/ghc-lib.cabal b/ghc-lib.cabal
--- a/ghc-lib.cabal
+++ b/ghc-lib.cabal
@@ -1,7 +1,7 @@
 cabal-version: >=1.22
 build-type: Simple
 name: ghc-lib
-version: 8.10.3.20201220
+version: 8.10.4.20210206
 license: BSD3
 license-file: LICENSE
 category: Development
@@ -80,7 +80,7 @@
         transformers == 0.5.*,
         process >= 1 && < 1.7,
         hpc == 0.6.*,
-        ghc-lib-parser == 8.10.3.20201220
+        ghc-lib-parser == 8.10.4.20210206
     build-tools: alex >= 3.1, happy >= 1.19.4
     other-extensions:
         BangPatterns
diff --git a/ghc-lib/stage0/lib/ghcversion.h b/ghc-lib/stage0/lib/ghcversion.h
--- a/ghc-lib/stage0/lib/ghcversion.h
+++ b/ghc-lib/stage0/lib/ghcversion.h
@@ -5,7 +5,7 @@
 # define __GLASGOW_HASKELL__ 810
 #endif
 
-#define __GLASGOW_HASKELL_PATCHLEVEL1__ 3
+#define __GLASGOW_HASKELL_PATCHLEVEL1__ 4
 
 #define MIN_VERSION_GLASGOW_HASKELL(ma,mi,pl1,pl2) (\
    ((ma)*100+(mi)) <  __GLASGOW_HASKELL__ || \