diff --git a/ShellCheck.cabal b/ShellCheck.cabal
index 9993ba9..8956ff5 100644
--- a/ShellCheck.cabal
+++ b/ShellCheck.cabal
@@ -35,7 +35,7 @@ custom-setup
   setup-depends:
     base    >= 4    && <5,
     process >= 1.0  && <1.7,
-    Cabal   >= 1.10 && <2.3
+    Cabal   >= 1.10 && <2.5
 
 source-repository head
     type: git
diff --git a/src/ShellCheck/AnalyzerLib.hs b/src/ShellCheck/AnalyzerLib.hs
index 5820cc7..de3498d 100644
--- a/src/ShellCheck/AnalyzerLib.hs
+++ b/src/ShellCheck/AnalyzerLib.hs
@@ -240,9 +240,10 @@ getParentTree t =
   where
     pre t = modify (first ((:) t))
     post t = do
-        (_:rest, map) <- get
-        case rest of []    -> put (rest, map)
-                     (x:_) -> put (rest, Map.insert (getId t) x map)
+        (x, map) <- get
+        case x of
+          _:rest -> case rest of []    -> put (rest, map)
+                                 (x:_) -> put (rest, Map.insert (getId t) x map)
 
 -- Given a root node, make a map from Id to Token
 getTokenMap :: Token -> Map.Map Id Token