diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,9 @@
+0.10.1.0:
+
+  Support building with GHC 9.2. The Swish.Datatype module
+  complains about non-exhaustive matches but it's in an
+  irrefutable match so I'm not sure how to avoid this.
+
 0.10.0.9:
 
   Support the semigroups 0.20 and initial support of the text 2.0
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -100,3 +100,9 @@
     % nix-shell
 	...
 	nix-shell% cabal test
+
+or
+
+    % nix-shell --argstr compiler ghc921
+	...
+	nix-shell% cabal test
diff --git a/default.nix b/default.nix
--- a/default.nix
+++ b/default.nix
@@ -1,1 +1,4 @@
-(import ./release.nix {}).exe
+{ compiler ? "ghc8107"
+}:
+
+(import ./release.nix { compiler = compiler; }).exe
diff --git a/shell.nix b/shell.nix
--- a/shell.nix
+++ b/shell.nix
@@ -1,1 +1,4 @@
-(import ./release.nix {}).shell
+{ compiler ? "ghc8107"
+}:
+
+(import ./release.nix { compiler = compiler; }).shell
diff --git a/src/Swish/RDF/Formatter/N3.hs b/src/Swish/RDF/Formatter/N3.hs
--- a/src/Swish/RDF/Formatter/N3.hs
+++ b/src/Swish/RDF/Formatter/N3.hs
@@ -7,7 +7,7 @@
 -- |
 --  Module      :  N3
 --  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin,
---                 2011, 2012, 2014, 2020 Douglas Burke
+--                 2011, 2012, 2014, 2020, 2021 Douglas Burke
 --  License     :  GPL V2
 --
 --  Maintainer  :  Douglas Burke
@@ -109,6 +109,7 @@
 import Control.Monad.State (State, modify, get, gets, put, runState)
 
 import Data.Char (isDigit)
+import Data.List (uncons)
 import Data.Word (Word32)
 
 #if (!defined(__GLASGOW_HASKELL__)) || (__GLASGOW_HASKELL__ < 710)
@@ -370,10 +371,19 @@
            , bNodesCheck   = bNodes
            }
 
+-- A version of uncons for a list which is not empty but we haven't
+-- encoded that invariant.
+--
+getNext :: [a] -> (a, [a])
+getNext xs = case uncons xs of
+               Just (a, as) -> (a, as)
+               Nothing -> error "Invariant broken: list is empty"
+
+
 nextSubject :: Formatter RDFLabel
 nextSubject = 
     changeState $ \st -> 
-        let (a,b):sbs = subjs st
+        let ((a,b), sbs) = getNext (subjs st)
             nst = st  { subjs = sbs
                       , props = b
                       , objs  = []
@@ -383,7 +393,7 @@
 nextProperty :: RDFLabel -> Formatter RDFLabel
 nextProperty _ =
     changeState $ \st ->
-        let (a,b):prs = props st
+        let ((a,b), prs) = getNext (props st)
             nst = st  { props = prs
                       , objs  = b
                       }
@@ -392,7 +402,7 @@
 nextObject :: RDFLabel -> RDFLabel -> Formatter RDFLabel
 nextObject _ _ =
     changeState $ \st ->
-        let ob:obs = objs st
+        let (ob, obs) = getNext (objs st)
             nst = st { objs = obs }
         in (ob, nst)
 
@@ -480,7 +490,7 @@
 --------------------------------------------------------------------------------
 --
 --  Copyright (c) 2003, Graham Klyne, 2009 Vasili I Galchin,
---    2011, 2012, 2014, 2020 Douglas Burke
+--    2011, 2012, 2014, 2020, 2021 Douglas Burke
 --  All rights reserved.
 --
 --  This file is part of Swish.
diff --git a/src/Swish/RDF/Formatter/Turtle.hs b/src/Swish/RDF/Formatter/Turtle.hs
--- a/src/Swish/RDF/Formatter/Turtle.hs
+++ b/src/Swish/RDF/Formatter/Turtle.hs
@@ -7,7 +7,7 @@
 -- |
 --  Module      :  Turtle
 --  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin,
---                 2011, 2012, 2013, 2014, 2018, 2019, 2020 Douglas Burke
+--                 2011, 2012, 2013, 2014, 2018, 2019, 2020, 2021 Douglas Burke
 --  License     :  GPL V2
 --
 --  Maintainer  :  Douglas Burke
@@ -97,6 +97,7 @@
 import Control.Monad.State (State, modify, gets, runState)
 
 import Data.Char (isDigit)
+import Data.List (uncons)
 import Data.Word (Word32)
 
 #if (!defined(__GLASGOW_HASKELL__)) || (__GLASGOW_HASKELL__ < 710)
@@ -289,10 +290,19 @@
            , bNodesCheck   = bNodes
            }
 
+-- A version of uncons for a list which is not empty but we haven't
+-- encoded that invariant.
+--
+getNext :: [a] -> (a, [a])
+getNext xs = case uncons xs of
+               Just (a, as) -> (a, as)
+               Nothing -> error "Invariant broken: list is empty"
+
+
 nextSubject :: Formatter RDFLabel
 nextSubject = 
     changeState $ \st -> 
-        let (a,b):sbs = subjs st
+        let ((a,b), sbs) = getNext (subjs st)
             nst = st  { subjs = sbs
                       , props = b
                       , objs  = []
@@ -302,7 +312,7 @@
 nextProperty :: RDFLabel -> Formatter RDFLabel
 nextProperty _ =
     changeState $ \st ->
-        let (a,b):prs = props st
+        let ((a,b), prs) = getNext (props st)
             nst = st  { props = prs
                       , objs  = b
                       }
@@ -311,7 +321,7 @@
 nextObject :: RDFLabel -> RDFLabel -> Formatter RDFLabel
 nextObject _ _ =
     changeState $ \st ->
-        let ob:obs = objs st
+        let (ob, obs) = getNext (objs st)
             nst = st { objs = obs }
         in (ob, nst)
 
@@ -381,7 +391,7 @@
 --------------------------------------------------------------------------------
 --
 --  Copyright (c) 2003, Graham Klyne, 2009 Vasili I Galchin,
---    2011, 2012, 2013, 2014, 2018, 2019, 2020 Douglas Burke
+--    2011, 2012, 2013, 2014, 2018, 2019, 2020, 2021 Douglas Burke
 --  All rights reserved.
 --
 --  This file is part of Swish.
diff --git a/src/Swish/RDF/Vocabulary.hs b/src/Swish/RDF/Vocabulary.hs
--- a/src/Swish/RDF/Vocabulary.hs
+++ b/src/Swish/RDF/Vocabulary.hs
@@ -6,7 +6,7 @@
 --------------------------------------------------------------------------------
 -- |
 --  Module      :  Vocabulary
---  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011, 2014 Douglas Burke
+--  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011, 2014, 2021 Douglas Burke
 --  License     :  GPL V2
 --
 --  Maintainer  :  Douglas Burke
@@ -71,6 +71,8 @@
 import Swish.RDF.Vocabulary.OWL
 import Swish.RDF.Vocabulary.XSD
 
+import Control.Monad (guard)
+
 import Data.Char (isDigit, isAsciiLower)
 import Data.List (isPrefixOf)
 import Data.List.NonEmpty (NonEmpty(..))
@@ -222,16 +224,19 @@
 -- or obey any other syntactical restriction than given above.
 -- 
 toLangTag :: T.Text -> Maybe LanguageTag
-toLangTag lbl = 
-    let tag = T.toLower lbl
-        toks = T.split (=='-') tag
-    in if all (\s -> let l = T.length s in l > 0 && l < 9) toks
-       then let primtag : subtags = toks
-            in if T.all isAsciiLower primtag && all (T.all (\c -> isAsciiLower c || isDigit c)) subtags
-               then Just $ LanguageTag lbl (NE.fromList toks)
-               else Nothing
-       else Nothing
+toLangTag lbl = do
+  let tag = T.toLower lbl
+      toks = T.split (=='-') tag
+  guard (all (\s -> let l = T.length s in l > 0 && l < 9) toks)
 
+  -- T.split can't return [] but the compiler doesn't know this
+  case toks of
+    primtag : subtags -> do
+      guard (T.all isAsciiLower primtag && all (T.all (\c -> isAsciiLower c || isDigit c)) subtags)
+      pure $ LanguageTag lbl (NE.fromList toks)
+
+    [] -> Nothing
+
 -- | Convert a language tag back into text form.
 fromLangTag :: LanguageTag -> T.Text
 fromLangTag (LanguageTag f _) = f
@@ -309,7 +314,7 @@
 
 --------------------------------------------------------------------------------
 --
---  Copyright (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011 Douglas Burke
+--  Copyright (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011, 2014, 2021 Douglas Burke
 --  All rights reserved.
 --
 --  This file is part of Swish.
diff --git a/swish.cabal b/swish.cabal
--- a/swish.cabal
+++ b/swish.cabal
@@ -1,5 +1,5 @@
 Name:               swish
-Version:            0.10.0.9
+Version:            0.10.1.0
 Stability:          experimental
 License:            LGPL-2.1
 License-file:       LICENSE 
@@ -94,7 +94,7 @@
 Library
    Default-Language:    Haskell2010
    Build-Depends:
-      base >= 4.8 && < 4.16,
+      base >= 4.8 && < 4.17,
       containers >= 0.5 && < 0.7,
       directory >= 1.0 && < 1.4,
       filepath >= 1.1 && < 1.5,
diff --git a/tests/RDFGraphTest.hs b/tests/RDFGraphTest.hs
--- a/tests/RDFGraphTest.hs
+++ b/tests/RDFGraphTest.hs
@@ -6,7 +6,7 @@
 --------------------------------------------------------------------------------
 -- |
 --  Module      :  RDFGraphTest
---  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011, 2012, 2013, 2014, 2017 Douglas Burke
+--  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011, 2012, 2013, 2014, 2017, 2021 Douglas Burke
 --  License     :  GPL V2
 --
 --  Maintainer  :  Douglas Burke
@@ -670,6 +670,11 @@
 --  Node generation tests
 ------------------------------------------------------------
 
+take3 :: [a] -> (a, a, a)
+take3 (a : b : c : _) = (a, b, c)
+take3 _ = error "Expected at least 3 elements"
+
+
 testNodeEq :: String -> RDFLabel -> RDFLabel -> Test
 testNodeEq = testCompare "testNodeEq:"
 
@@ -678,10 +683,10 @@
 tnn02 = newNode  b1 [b1,b3,v1,v2]
 
 tnn03, tnn04, tnn05 :: RDFLabel
-(tnn03 : tnn04 : tnn05 : _ ) = newNodes b1 [b1, b3, v1, v2]
+(tnn03, tnn04, tnn05) = take3 $ newNodes b1 [b1, b3, v1, v2]
 
 tnn06, tnn07, tnn08 :: RDFLabel
-(tnn06 : tnn07 : tnn08 : _ ) = newNodes s1 [b1,b3,v1,v2,tnns3]
+(tnn06, tnn07, tnn08) = take3 $ newNodes s1 [b1,b3,v1,v2,tnns3]
 
 tnn09 :: RDFLabel
 tnn09 = newNodes l1 [b1,b3,v1,v2,tnns3] !! 2
@@ -1609,7 +1614,7 @@
 --------------------------------------------------------------------------------
 --
 --  Copyright (c) 2003, Graham Klyne, 2009 Vasili I Galchin,
---    2011, 2012, 2013, 2014 Douglas Burke  
+--    2011, 2012, 2013, 2014, 2017, 2021 Douglas Burke  
 --  All rights reserved.
 --
 --  This file is part of Swish.
diff --git a/tests/RDFProofContextTest.hs b/tests/RDFProofContextTest.hs
--- a/tests/RDFProofContextTest.hs
+++ b/tests/RDFProofContextTest.hs
@@ -6,7 +6,7 @@
 --------------------------------------------------------------------------------
 -- |
 --  Module      :  RDFProofContextTest
---  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011, 2012, 2013, 2014 Douglas Burke
+--  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011, 2012, 2013, 2014, 2021 Douglas Burke
 --  License     :  GPL V2
 --
 --  Maintainer  :  Douglas Burke
@@ -110,15 +110,20 @@
 makeSName :: String -> ScopedName
 makeSName nam = makeNSScopedName ns (fromJust (newLName (T.pack loc)))
     where
-        (pre,_:loc) = break (==':') nam
-        ns = case pre of
-            "rs_rdf"  -> scopeRDF
-            "rs_rdfs" -> scopeRDFS
-            "rs_rdfd" -> scopeRDFD
-            "xsd_integer" -> namespaceXsdType "integer"
-            "xsd_string"  -> namespaceXsdType "string"
-            _ -> error $ "makeSName: Unrecognized prefix in rule name: " ++ nam
+      err = error $ "makeSName: Unrcognized prefix in rule name: " ++ nam
+      (pre, post) = break (==':') nam
+      loc = case post of
+        "" -> err
+        _:loc' -> loc'
 
+      ns = case pre of
+             "rs_rdf"  -> scopeRDF
+             "rs_rdfs" -> scopeRDFS
+             "rs_rdfd" -> scopeRDFD
+             "xsd_integer" -> namespaceXsdType "integer"
+             "xsd_string"  -> namespaceXsdType "string"
+             _ -> err
+
 --  Common definitions
 
 toURI :: String -> URI
@@ -669,7 +674,7 @@
 --------------------------------------------------------------------------------
 --
 --  Copyright (c) 2003, Graham Klyne, 2009 Vasili I Galchin,
---    2011, 2012, 2013 Douglas Burke
+--    2011, 2012, 2013, 2014, 2021 Douglas Burke
 --  All rights reserved.
 --
 --  This file is part of Swish.
diff --git a/tests/RDFQueryTest.hs b/tests/RDFQueryTest.hs
--- a/tests/RDFQueryTest.hs
+++ b/tests/RDFQueryTest.hs
@@ -6,7 +6,7 @@
 --------------------------------------------------------------------------------
 -- |
 --  Module      :  RDFQueryTest
---  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011, 2012, 2013, 2014, 2018 Douglas Burke
+--  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011, 2012, 2013, 2014, 2018, 2021 Douglas Burke
 --  License     :  GPL V2
 --
 --  Maintainer  :  Douglas Burke
@@ -120,6 +120,16 @@
 result11b = prefix1 `mappend` "ex:s2  ex:r  \"lit1\" . \n"
 result11c = prefix1 `mappend` "[ ex:r ex:o3 ] . \n"
 
+-- Avoid incomplete-coverage warnings from ghc 9.2
+get1 :: [x] -> x
+get1 [x] = x
+get1 _ = error "Invalid response - not a singleton"
+
+get2 :: [x] -> (x, x)
+get2 [x, y] = (x, y)
+get2 _ = error "Invalid response - not a pair"
+
+
 var11 :: [RDFVarBinding]
 var11 = rdfQueryFind query11 graph1
 
@@ -721,8 +731,9 @@
 res44 = rdfQueryBackSubs var44 result44
 
 res44_1, res44_2 :: [(RDFGraph, [RDFLabel])]
-[res44_1,res44_2] = res44
+(res44_1, res44_2) = get2 res44
 
+
 --  test45:  multiple substitutions used together
 --
 --  (?a daughter ?b, ?a son ?c) => ?b brother ?c
@@ -769,10 +780,10 @@
 res45 = rdfQueryBackSubs var45 result45
 
 res45_1 :: [(RDFGraph, [RDFLabel])]
-[res45_1] = res45
+res45_1 = get1 $ res45
 
 res45_11, res45_12 :: (RDFGraph, [RDFLabel])
-[res45_11,res45_12] = res45_1
+(res45_11, res45_12) = get2 $ res45_1
 
 --  test46:  multiple ways to get solution
 --
@@ -820,11 +831,11 @@
 res46 = rdfQueryBackSubs var46 result46
 
 res46_1, res46_2 :: [(RDFGraph, [RDFLabel])]
-[res46_1,res46_2] = res46
+(res46_1, res46_2) = get2 res46
 
 res46_11, res46_21 :: (RDFGraph, [RDFLabel])
-[res46_11] = res46_1
-[res46_21] = res46_2
+res46_11 = get1 res46_1
+res46_21 = get1 res46_2
 
 --  test47:  multiple ways to multiple solutions
 --
@@ -909,16 +920,19 @@
 res47 = rdfQueryBackSubs var47 result47
 
 res47_1, res47_2, res47_3, res47_4 :: [(RDFGraph, [RDFLabel])]
-[res47_1,res47_2,res47_3,res47_4] = res47
+(res47_1, res47_2, res47_3, res47_4) = case res47 of
+  [a, b, c, d] -> (a, b, c, d)
+  _ -> error "Expected 4 answers"
+  
 
 res47_11, res47_12,
   res47_21, res47_22, 
   res47_31, res47_32, 
   res47_41, res47_42 :: (RDFGraph, [RDFLabel])
-[res47_11,res47_12] = res47_1
-[res47_21,res47_22] = res47_2
-[res47_31,res47_32] = res47_3
-[res47_41,res47_42] = res47_4
+(res47_11, res47_12) = get2 res47_1
+(res47_21, res47_22) = get2 res47_2
+(res47_31, res47_32) = get2 res47_3
+(res47_41, res47_42) = get2 res47_4
 
 --  test48:  redundant multiple ways to get solution
 --
@@ -959,11 +973,11 @@
 res48 = rdfQueryBackSubs var48 result48
 
 res48_1, res48_2 :: [(RDFGraph, [RDFLabel])]
-[res48_1,res48_2] = res48
+(res48_1, res48_2) = get2 res48
 
 res48_11, res48_21 :: (RDFGraph, [RDFLabel])
-[res48_11] = res48_1
-[res48_21] = res48_2
+res48_11 = get1 res48_1
+res48_21 = get1 res48_2
 
 -- test49: goal not satisfiable by rule
 --
@@ -1028,11 +1042,11 @@
 res50 = rdfQueryBackSubs var50 result50
 
 res50_1, res50_2 :: [(RDFGraph, [RDFLabel])]
-[res50_1,res50_2] = res50
+(res50_1, res50_2) = get2 res50
 
 res50_11, res50_21 :: (RDFGraph, [RDFLabel])
-[res50_11] = res50_1
-[res50_21] = res50_2
+res50_11 = get1 res50_1
+res50_21 = get1 res50_2
 
 filter50 :: RDFVarBindingFilter
 filter50 = varFilterNE (Var "b") (Var "c")
@@ -1196,7 +1210,7 @@
 res61          = rdfQueryBackSubsBlank var61 result61
 
 res61a1, res61a2, res61a :: RDFGraph
-[[res61a1,res61a2]] = res61
+(res61a1, res61a2) = get2 $ get1 $ res61
 res61a = merge res61a1 res61a2
 
 --  2. Instance query against 'graph2'
@@ -1210,7 +1224,7 @@
 res63 = rdfQuerySubs var62 res61a
 
 res63a :: RDFGraph
-[res63a] = res63
+res63a = get1 res63
 
 --  4. Repeat instance query against 'graph2'
 --     Query bindings should be null.
@@ -1219,7 +1233,7 @@
 var64 = rdfQueryInstance res63a graph2
 
 var64a :: RDFVarBinding
-[var64a] = var64
+var64a = get1 var64
 
 test6 :: Test
 test6 = 
@@ -1657,7 +1671,7 @@
 --------------------------------------------------------------------------------
 --
 --  Copyright (c) 2003, Graham Klyne, 2009 Vasili I Galchin,
---    2011, 2012, 2013 Douglas Burke  
+--    2011, 2012, 2013, 2014, 2018, 2021 Douglas Burke  
 --  All rights reserved.
 --
 --  This file is part of Swish.
diff --git a/tests/VarBindingTest.hs b/tests/VarBindingTest.hs
--- a/tests/VarBindingTest.hs
+++ b/tests/VarBindingTest.hs
@@ -5,7 +5,7 @@
 --------------------------------------------------------------------------------
 -- |
 --  Module      :  VarBindingTest
---  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011, 2013 Douglas Burke
+--  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin, 2011, 2013, 2021 Douglas Burke
 --  License     :  GPL V2
 --
 --  Maintainer  :  Douglas Burke
@@ -191,9 +191,15 @@
            }
 
 
+-- Avoid pattern-match errors from ghc 9.2
+get1 :: [a] -> a
+get1 [x] = x
+get1 _ = error "Expected single-element list"
+
+
 vb1m1, vb2m1 :: VarBinding String Int
-[vb1m1] = vbmApply vbm1 [vb1m]
-[vb2m1] = vbmApply vbm1 [vb2m]
+vb1m1 = get1 $ vbmApply vbm1 [vb1m]
+vb2m1 = get1 $ vbmApply vbm1 [vb2m]
 
 -- Filter for bindings that define a
 vbm2 :: VarBindingModify String Int
@@ -314,9 +320,14 @@
     , vbmUsage = [[],["a"],["c"],["d"]]
     }
 
+getJust :: Maybe x -> x
+getJust (Just x) = x
+getJust _ = error "Expected something, got Nothing"
+
+
 vbm34, vbm43 :: VarBindingModify String Int
-Just vbm34 = vbmCompose vbm3 vbm4
-Just vbm43 = vbmCompose vbm4 vbm3
+vbm34 = getJust $ vbmCompose vbm3 vbm4
+vbm43 = getJust $ vbmCompose vbm4 vbm3
 
 vbm34vocab, vbm43vocab :: [String]
 vbm34vocab = [ "a", "b", "c", "d"]
@@ -403,11 +414,11 @@
 jvbmid1    = vbmCompose varBindingId vbm1
 
 vb1m1id, vb2m1id, vb1mid1, vb2mid1 :: VarBinding String Int
-[vb1m1id] = vbmApply (fromJust jvbm1id) [vb1m]
-[vb2m1id] = vbmApply (fromJust jvbm1id) [vb2m]
+vb1m1id = get1 $ vbmApply (fromJust jvbm1id) [vb1m]
+vb2m1id = get1 $ vbmApply (fromJust jvbm1id) [vb2m]
 
-[vb1mid1] = vbmApply (fromJust jvbmid1) [vb1m]
-[vb2mid1] = vbmApply (fromJust jvbmid1) [vb2m]
+vb1mid1 = get1 $ vbmApply (fromJust jvbmid1) [vb1m]
+vb2mid1 = get1 $ vbmApply (fromJust jvbmid1) [vb2m]
 
 testVarComposeSuite :: Test
 testVarComposeSuite = 
@@ -797,7 +808,7 @@
 --------------------------------------------------------------------------------
 --
 --  Copyright (c) 2003, Graham Klyne, 2009 Vasili I Galchin,
---      2011, 2013 Douglas Burke
+--      2011, 2013, 2021 Douglas Burke
 --  All rights reserved.
 --
 --  This file is part of Swish.