diff --git a/src/SExp.res b/src/SExp.res
index 1b8d1cb..448d635 100644
--- a/src/SExp.res
+++ b/src/SExp.res
@@ -20,6 +20,7 @@ module ConstSymbol: SExpFunc.SYMBOL with type t = string = {
   let ghost = ""
   let substDeBruijn = (name, _, ~from as _) => name
   let unifiesWithAnything = _ => false
+  let upshift = (t, _, ~from as _=?) => t
 }
 
 include SExpFunc.Make(ConstSymbol)
diff --git a/src/SExpFunc.res b/src/SExpFunc.res
index 9d825a3..408b145 100644
--- a/src/SExpFunc.res
+++ b/src/SExpFunc.res
@@ -5,6 +5,7 @@ module type SYMBOL = {
   let prettyPrint: (t, ~scope: array<string>) => string
   let parse: (string, ~scope: array<string>, ~gen: ref<int>=?) => result<(t, string), string>
   let substitute: (t, subst) => t
+  let upshift: (t, int, ~from: int=?) => t
   // used for when trying to substitute a variable of the wrong type
   let lowerVar: int => t
   let lowerSchematic: (int, array<int>) => t
@@ -194,7 +195,7 @@ module Make = (Symbol: SYMBOL): {
     }
   let rec upshift = (term: t, amount: int, ~from: int=0) =>
     switch term {
-    | Symbol(_) => term
+    | Symbol(s) => Symbol(s->Symbol.upshift(amount, ~from))
     | Compound({subexps}) => Compound({subexps: Array.map(subexps, x => upshift(x, amount, ~from))})
     | Var({idx}) =>
       Var({
diff --git a/src/StringSExp.res b/src/StringSExp.res
index 73dcaf3..9b30da8 100644
--- a/src/StringSExp.res
+++ b/src/StringSExp.res
@@ -37,6 +37,11 @@ module StringSymbol: SExpFunc.SYMBOL with type t = stringSymbol = {
       }
     | ConstS(s) => ConstS(s)
     }
+  let upshift = (s, amount: int, ~from=?) =>
+    switch s {
+    | StringS(s) => StringS(s->StringTerm.upshift(amount, ~from?))
+    | ConstS(s) => ConstS(s)
+    }
   let lowerVar = idx => StringS([StringTerm.Var({idx: idx})])
   let lowerSchematic = (schematic, allowed) => StringS([StringTerm.Schematic({schematic, allowed})])
   let ghost = StringS([StringTerm.Ghost])