diff --git a/flap/src/hopix/hopixTypechecker.ml b/flap/src/hopix/hopixTypechecker.ml
index 017134e..c07e501 100644
--- a/flap/src/hopix/hopixTypechecker.ml
+++ b/flap/src/hopix/hopixTypechecker.ml
@@ -191,7 +191,13 @@ and synth_assign
   :  HopixTypes.typing_environment -> expression Position.located
   -> expression Position.located -> HopixTypes.aty
   =
-  fun tenv ref expr -> failwith "Students! This is your job! (synth_assign)"
+  fun tenv ref expr ->
+  let refty = synth_expression tenv ref in
+  match HopixTypes.destruct_reference_type expr.position refty with
+  | expected ->
+    let given = synth_expression tenv expr in
+    check_equal_types expr.position ~expected ~given;
+    HopixTypes.hunit
 
 and synth_read
   : HopixTypes.typing_environment -> expression Position.located -> HopixTypes.aty