--- a/devtools/client/webconsole/jsterm.js
+++ b/devtools/client/webconsole/jsterm.js
@@ -581,16 +581,21 @@ JSTerm.prototype = {
    *        option is not used, then the variables view opens in the sidebar.
    *        - autofocus: optional boolean, |true| if you want to give focus to
    *        the variables view window after open, |false| otherwise.
    * @return object
    *         A promise object that is resolved when the variables view has
    *         opened. The new variables view instance is given to the callbacks.
    */
   openVariablesView: function (options) {
+    // Bail out if the side bar doesn't exist.
+    if (!this.hud.document.querySelector("#webconsole-sidebar")) {
+      return Promise.resolve(null);
+    }
+
     let onContainerReady = (window) => {
       let container = window.document.querySelector("#variables");
       let view = this._variablesView;
       if (!view || options.targetElement) {
         let viewOptions = {
           container: container,
           hideFilterInput: options.hideFilterInput,
         };