diff --git a/exe/Options.idr b/exe/Options.idr
index 58b545b..7698730 100644
--- a/exe/Options.idr
+++ b/exe/Options.idr
@@ -7,6 +7,7 @@ import System.File
 import System.Term
 import Derive.Prelude
 
+%default total
 %language ElabReflection
 
 public export
@@ -63,20 +64,14 @@ toOutFile ""  = Ok {outFile := None}
 toOutFile "-" = Ok {outFile := Stdout}
 toOutFile f   = Ok {outFile := File f}
 
-private
-phaseName : Phase -> String
-phaseName Parse = "parse"
-phaseName Check = "check"
-phaseName Erase = "erase"
-
 private
 toPhase : String -> OptAction
-toPhase str = case toLower str of
-  "parse" => Ok {until := Just Parse}
-  "check" => Ok {until := Just Check}
-  "erase" => Ok {until := Just Erase}
-  _       => Err "unknown phase name \{show str}\nphases: \{phaseNames}"
-where phaseNames = joinBy ", " $ map phaseName allPhases
+toPhase str =
+  let lstr = toLower str in
+  case find (\p => toLower (show p) == lstr) allPhases of
+    Just p  => Ok {until := Just p}
+    Nothing => Err "unknown phase name \{show str}\nphases: \{phaseNames}"
+where phaseNames = joinBy ", " $ map (toLower . show) allPhases
 
 private
 toWidth : String -> OptAction