diff --git a/src/Bergamot/Rules.elm b/src/Bergamot/Rules.elm
index 407653f..aa8a471 100644
--- a/src/Bergamot/Rules.elm
+++ b/src/Bergamot/Rules.elm
@@ -135,6 +135,9 @@ builtinRules t =
         Call "str" [StringLit s] ->
             MkProofTree { name = "BuiltinStr", conclusion = t, premises = [] }
             |> pure
+        Call "sym" [Call s []] ->
+            MkProofTree { name = "BuiltinSym", conclusion = t, premises = [] }
+            |> pure
         Call "tostring" [IntLit i, Var output] ->
             liftUnification unify (Var output) (StringLit (String.fromInt i))
             |> map (\_ -> MkProofTree { name = "BuiltinToString", conclusion = t, premises = []})