diff --git a/flap/src/hopix/hopixTypechecker.ml b/flap/src/hopix/hopixTypechecker.ml
index 5abe051..bf4ccde 100644
--- a/flap/src/hopix/hopixTypechecker.ml
+++ b/flap/src/hopix/hopixTypechecker.ml
@@ -177,7 +177,9 @@ and synth_define
   :  HopixTypes.typing_environment -> value_definition -> expression Position.located
   -> HopixTypes.aty
   =
-  fun tenv vdef expr -> failwith "Students! This is your job! (synth_define)"
+  fun tenv vdef expr ->
+  let tenv = check_value_definition tenv vdef in
+  synth_expression tenv expr
 
 and synth_ref
   : HopixTypes.typing_environment -> expression Position.located -> HopixTypes.aty