diff --git a/inst/rkward/plugins/common/common_functions.js b/inst/rkward/plugins/common/common_functions.js
index ab5a424..d989625 100644
--- a/inst/rkward/plugins/common/common_functions.js
+++ b/inst/rkward/plugins/common/common_functions.js
@@ -3,6 +3,6 @@ function getDataframe(vars) {
     if (Array.isArray(vars)) {
         return vars.join().split('[[')[0];
     } else {
-        return vars.split('[[')[0];
+        return vars.toString().split('[[')[0];
     }
 }