diff --git a/tests/Tests/DimEq.idr b/tests/Tests/DimEq.idr
index d21b451..ecebc5e 100644
--- a/tests/Tests/DimEq.idr
+++ b/tests/Tests/DimEq.idr
@@ -16,9 +16,9 @@ import Data.So
 
 private
 prettyDimEq' : {default Arg prec : PPrec} -> NContext d -> DimEq d -> Doc HL
-prettyDimEq' ds eqs = case ds of
-  [<] => "·"
-  _   => runPrettyWith False (toSnocList' ds) [<] $ withPrec prec $ prettyM eqs
+prettyDimEq' [<] (C _) = "·"
+prettyDimEq' ds eqs =
+  runPrettyWith False (toSnocList' ds) [<] $ withPrec prec $ prettyM eqs
 
 private
 testPrettyD : NContext d -> DimEq d -> (str : String) ->