diff --git a/webapp/src/components/labThingsComponents/actionButton.vue b/webapp/src/components/labThingsComponents/actionButton.vue
index 7efbbbc9..1defd4dd 100644
--- a/webapp/src/components/labThingsComponents/actionButton.vue
+++ b/webapp/src/components/labThingsComponents/actionButton.vue
@@ -171,6 +171,26 @@ export default {
   },
 
   mounted() {
+    //Define .from_index() as a custom function, working similar to .at()
+    //For backwards compatibility, not using in-built .at() until updates to Connect
+    function from_index(n) {
+      // ToInteger() abstract op
+      n = Math.trunc(n) || 0;
+      // Allow negative indexing from the end
+      if (n < 0) n += this.length;
+      // OOB access is guaranteed to return undefined
+      if (n < 0 || n >= this.length) return undefined;
+      // Otherwise, this is just normal property access
+      return this[n];
+    }
+  const TypedArray = Reflect.getPrototypeOf(Int8Array);
+  for (const C of [Array, String, TypedArray]) {
+      Object.defineProperty(C.prototype, "from_index",
+        { value: from_index,
+          writable: true,
+          enumerable: false,
+          configurable: true });
+    }
     // Check for already running tasks
     if (this.taskStarted != true) {
       this.checkExistingTasks();
@@ -299,14 +319,14 @@ export default {
               if (!this.progress) this.progress = 1;
               // Test whether the log is empty or the most recent message is not from an error
               // If so, return a default message
-              if (response.data.log.length == 0 | response.data.log.at(-1).levelname != "ERROR") {
+              if (response.data.log.length == 0 | response.data.log.from_index(-1).levelname != "ERROR") {
                 var message = "Unexpected error, please check the logs";
               }
               // As LabThings Actions add the message from any raised exception to the log, the
               // last message in the log is the message from the Exception.
               //If the Exception was raised with no message, use a default.
               else {
-                message = response.data.log.at(-1).message||"Unexpected error, please check the logs";
+                message = response.data.log.from_index(-1).message||"Unexpected error, please check the logs";
               }
               // Raise an Error with the chosen message
               reject(new Error(message));