diff --git a/lisp.c b/lisp.c
index 345ffad..3ebe71f 100644
--- a/lisp.c
+++ b/lisp.c
@@ -945,7 +945,7 @@ static Value builtin_define(Value *env, Value ident, Value expr)
 
 static Value builtin_set(Value *env, Value ident, Value expr)
 {
-    expect_type(TYPE_SYMBOL, ident, "set");
+    expect_type(TYPE_SYMBOL, ident, "set!");
 
     Value found = alist_find(*env, ident);
     if (found == Qnil)