diff --git a/shared/static/scripts/sx.js b/shared/static/scripts/sx.js
index a94ff97..09a6310 100644
--- a/shared/static/scripts/sx.js
+++ b/shared/static/scripts/sx.js
@@ -313,7 +313,7 @@
   PRIMITIVES["list?"] = function (x) { return Array.isArray(x); };
   PRIMITIVES["dict?"] = function (x) { return x !== null && typeof x === "object" && !Array.isArray(x) && !x._sym && !x._kw; };
   PRIMITIVES["empty?"] = function (c) { return !c || (Array.isArray(c) ? c.length === 0 : Object.keys(c).length === 0); };
-  PRIMITIVES["contains?"] = function (c, k) { return Array.isArray(c) ? c.indexOf(k) !== -1 : k in c; };
+  PRIMITIVES["contains?"] = function (c, k) { return typeof c === "string" ? c.indexOf(k) !== -1 : Array.isArray(c) ? c.indexOf(k) !== -1 : k in c; };
   PRIMITIVES["odd?"] = function (n) { return n % 2 !== 0; };
   PRIMITIVES["even?"] = function (n) { return n % 2 === 0; };
   PRIMITIVES["zero?"] = function (n) { return n === 0; };
diff --git a/shared/sx/primitives.py b/shared/sx/primitives.py
index 9dd202b..ad74440 100644
--- a/shared/sx/primitives.py
+++ b/shared/sx/primitives.py
@@ -196,6 +196,8 @@ def prim_is_empty(coll: Any) -> bool:
 
 @register_primitive("contains?")
 def prim_contains(coll: Any, key: Any) -> bool:
+    if isinstance(coll, str):
+        return str(key) in coll
     if isinstance(coll, dict):
         k = key.name if isinstance(key, Keyword) else key
         return k in coll