diff --git a/js/src/output.ts b/js/src/output.ts
index cfaf427..c92feb3 100644
--- a/js/src/output.ts
+++ b/js/src/output.ts
@@ -113,29 +113,32 @@ class IPyWidgetOutput extends Shiny.OutputBinding {
     this._maybeResize(lmWidget);
   }
   _maybeResize(lmWidget: HTMLElement): void {
-    const impl = lmWidget.children[0];
-    if (impl.children.length > 0) {
-      return this._doResize(impl);
+    if (this._hasImplementation(lmWidget)) {
+      return this._doResize();
     }
 
     // Some widget implementation (e.g., ipyleaflet, pydeck) won't actually
     // have rendered to the DOM at this point, so wait until they do
     const mo = new MutationObserver((mutations) => {
-      if (impl.children.length > 0) {
+      if (this._hasImplementation(lmWidget)) {
         mo.disconnect();
-        this._doResize(impl);
+        this._doResize();
       }
     });
 
-    mo.observe(impl, {childList: true});
+    mo.observe(lmWidget, {childList: true});
   }
-  _doResize(impl: Element): void {
+  _doResize(): void {
     // Trigger resize event to force layout (setTimeout() is needed for altair)
     // TODO: debounce this call?
     setTimeout(() => {
       window.dispatchEvent(new Event('resize'))
     }, 0);
   }
+  _hasImplementation(lmWidget: HTMLElement): boolean {
+    const impl = lmWidget.children[0];
+    return impl && impl.children.length > 0;
+  }
 }
 
 Shiny.outputBindings.register(new IPyWidgetOutput(), "shiny.IPyWidgetOutput");
diff --git a/shinywidgets/static/output.js b/shinywidgets/static/output.js
index 60faa5e..fc2289a 100644
--- a/shinywidgets/static/output.js
+++ b/shinywidgets/static/output.js
@@ -36,7 +36,7 @@ eval("__webpack_require__.r(__webpack_exports__);\n/* harmony export */ __webpac
   \***********************/
 /***/ ((__unused_webpack_module, __webpack_exports__, __webpack_require__) => {
 
-eval("__webpack_require__.r(__webpack_exports__);\n/* harmony import */ var _jupyter_widgets_html_manager__WEBPACK_IMPORTED_MODULE_0__ = __webpack_require__(/*! @jupyter-widgets/html-manager */ \"@jupyter-widgets/html-manager\");\n/* harmony import */ var _jupyter_widgets_html_manager__WEBPACK_IMPORTED_MODULE_0___default = /*#__PURE__*/__webpack_require__.n(_jupyter_widgets_html_manager__WEBPACK_IMPORTED_MODULE_0__);\n/* harmony import */ var _comm__WEBPACK_IMPORTED_MODULE_1__ = __webpack_require__(/*! ./comm */ \"./src/comm.ts\");\n/* harmony import */ var _utils__WEBPACK_IMPORTED_MODULE_2__ = __webpack_require__(/*! ./utils */ \"./src/utils.ts\");\nvar _a;\n\n\n\n/******************************************************************************\n * Define a custom HTMLManager for use with Shiny\n ******************************************************************************/\nclass OutputManager extends _jupyter_widgets_html_manager__WEBPACK_IMPORTED_MODULE_0__.HTMLManager {\n    // In a soon-to-be-released version of @jupyter-widgets/html-manager,\n    // display_view()'s first \"dummy\" argument will be removed... this shim simply\n    // makes it so that our manager can work with either version\n    // https://github.com/jupyter-widgets/ipywidgets/commit/159bbe4#diff-45c126b24c3c43d2cee5313364805c025e911c4721d45ff8a68356a215bfb6c8R42-R43\n    async display_view(view, options) {\n        const n_args = super.display_view.length;\n        if (n_args === 3) {\n            return super.display_view({}, view, options);\n        }\n        else {\n            // @ts-ignore\n            return super.display_view(view, options);\n        }\n    }\n}\n// Define our own custom module loader for Shiny\nconst shinyRequireLoader = async function (moduleName, moduleVersion) {\n    // shiny provides require.js and also sets `define.amd=false` to prevent <script>s\n    // with UMD loaders from triggering anonymous define() errors. shinywidgets should\n    // generally be able to avoid anonymous define errors though since there should only\n    // be one 'main' anonymous define() for the widget's module (located in a JS file that\n    // we've already require.config({paths: {...}})ed; and in that case, requirejs adds a\n    // data-requiremodule attribute to the <script> tag that shiny's custom define will\n    // recognize and use as the name).)\n    const oldAmd = window.define.amd;\n    // The is the original value for define.amd that require.js sets\n    window.define.amd = { jQuery: true };\n    // Store jQuery global since loading we load a module, it may overwrite it\n    // (qgrid is one good example)\n    const old$ = window.$;\n    const oldJQ = window.jQuery;\n    if (moduleName === 'qgrid') {\n        // qgrid wants to use base/js/dialog (if it's available) for full-screen tables\n        // https://github.com/quantopian/qgrid/blob/877b420/js/src/qgrid.widget.js#L11-L16\n        // Maybe that's worth supporting someday, but for now, we define it to be nothing\n        // to avoid require('qgrid') from producing an error\n        window.define(\"base/js/dialog\", [], function () { return null; });\n    }\n    return (0,_jupyter_widgets_html_manager__WEBPACK_IMPORTED_MODULE_0__.requireLoader)(moduleName, moduleVersion).finally(() => {\n        window.define.amd = oldAmd;\n        window.$ = old$;\n        window.jQuery = oldJQ;\n    });\n};\nconst manager = new OutputManager({ loader: shinyRequireLoader });\n/******************************************************************************\n* Define the Shiny binding\n******************************************************************************/\n// Ideally we'd extend Shiny's HTMLOutputBinding, but the implementation isn't exported\nclass IPyWidgetOutput extends Shiny.OutputBinding {\n    find(scope) {\n        return $(scope).find(\".shiny-ipywidget-output\");\n    }\n    onValueError(el, err) {\n        Shiny.unbindAll(el);\n        this.renderError(el, err);\n    }\n    async renderValue(el, data) {\n        // Allow for a None/null value to hide the widget (css inspired by htmlwidgets)\n        if (!data) {\n            el.style.visibility = \"hidden\";\n            return;\n        }\n        else {\n            el.style.visibility = \"inherit\";\n        }\n        // Only forward the potential to fill if `output_widget(fillable=True)`\n        // _and_ the widget instance wants to fill\n        const fill = data.fill && el.classList.contains(\"html-fill-container\");\n        if (fill)\n            el.classList.add(\"forward-fill-potential\");\n        // At this time point, we should've already handled an 'open' message, and so\n        // the model should be ready to use\n        const model = await manager.get_model(data.model_id);\n        if (!model) {\n            throw new Error(`No model found for id ${data.model_id}`);\n        }\n        const view = await manager.create_view(model, {});\n        await manager.display_view(view, { el: el });\n        // Don't allow more than one .lmWidget container, which can happen\n        // when the view is displayed more than once\n        // TODO: It's probably better to get view(s) from m.views and .remove() them\n        while (el.childNodes.length > 1) {\n            el.removeChild(el.childNodes[0]);\n        }\n        // The ipywidgets container (.lmWidget)\n        const lmWidget = el.children[0];\n        this._maybeResize(lmWidget);\n    }\n    _maybeResize(lmWidget) {\n        const impl = lmWidget.children[0];\n        if (impl.children.length > 0) {\n            return this._doResize(impl);\n        }\n        // Some widget implementation (e.g., ipyleaflet, pydeck) won't actually\n        // have rendered to the DOM at this point, so wait until they do\n        const mo = new MutationObserver((mutations) => {\n            if (impl.children.length > 0) {\n                mo.disconnect();\n                this._doResize(impl);\n            }\n        });\n        mo.observe(impl, { childList: true });\n    }\n    _doResize(impl) {\n        // Trigger resize event to force layout (setTimeout() is needed for altair)\n        // TODO: debounce this call?\n        setTimeout(() => {\n            window.dispatchEvent(new Event('resize'));\n        }, 0);\n    }\n}\nShiny.outputBindings.register(new IPyWidgetOutput(), \"shiny.IPyWidgetOutput\");\n// Due to the way HTMLManager (and widget implementations) get loaded (via\n// require.js), the binding registration above can happen _after_ Shiny has\n// already bound the DOM, especially in the dynamic UI case (i.e., output_binding()'s\n// dependencies don't come in until after initial page load). And, in the dynamic UI\n// case, UI is rendered asychronously via Shiny.shinyapp.taskQueue, so if it exists,\n// we probably need to re-bind the DOM after the taskQueue is done.\nconst taskQueue = (_a = Shiny === null || Shiny === void 0 ? void 0 : Shiny.shinyapp) === null || _a === void 0 ? void 0 : _a.taskQueue;\nif (taskQueue) {\n    taskQueue.enqueue(() => Shiny.bindAll(document.body));\n}\n/******************************************************************************\n* Handle messages from the server-side Widget\n******************************************************************************/\n// Initialize the comm and model when a new widget is created\n// This is basically our version of https://github.com/jupyterlab/jupyterlab/blob/d33de15/packages/services/src/kernel/default.ts#L1144-L1176\nShiny.addCustomMessageHandler(\"shinywidgets_comm_open\", (msg_txt) => {\n    setBaseURL();\n    const msg = (0,_utils__WEBPACK_IMPORTED_MODULE_2__.jsonParse)(msg_txt);\n    Shiny.renderDependencies(msg.content.html_deps);\n    const comm = new _comm__WEBPACK_IMPORTED_MODULE_1__.ShinyComm(msg.content.comm_id);\n    manager.handle_comm_open(comm, msg);\n});\n// Handle any mutation of the model (e.g., add a marker to a map, without a full redraw)\n// Basically out version of https://github.com/jupyterlab/jupyterlab/blob/d33de15/packages/services/src/kernel/default.ts#L1200-L1215\nShiny.addCustomMessageHandler(\"shinywidgets_comm_msg\", (msg_txt) => {\n    const msg = (0,_utils__WEBPACK_IMPORTED_MODULE_2__.jsonParse)(msg_txt);\n    manager.get_model(msg.content.comm_id).then(m => {\n        // @ts-ignore for some reason IClassicComm doesn't have this method, but we do\n        m.comm.handle_msg(msg);\n    });\n});\n// TODO: test that this actually works\nShiny.addCustomMessageHandler(\"shinywidgets_comm_close\", (msg_txt) => {\n    const msg = (0,_utils__WEBPACK_IMPORTED_MODULE_2__.jsonParse)(msg_txt);\n    manager.get_model(msg.content.comm_id).then(m => {\n        // @ts-ignore for some reason IClassicComm doesn't have this method, but we do\n        m.comm.handle_close(msg);\n    });\n});\n// Our version of https://github.com/jupyter-widgets/widget-cookiecutter/blob/9694718/%7B%7Bcookiecutter.github_project_name%7D%7D/js/lib/extension.js#L8\nfunction setBaseURL(x = '') {\n    const base_url = document.querySelector('body').getAttribute('data-base-url');\n    if (!base_url) {\n        document.querySelector('body').setAttribute('data-base-url', x);\n    }\n}\n\n\n//# sourceURL=webpack://@jupyter-widgets/shiny-embed-manager/./src/output.ts?");
+eval("__webpack_require__.r(__webpack_exports__);\n/* harmony import */ var _jupyter_widgets_html_manager__WEBPACK_IMPORTED_MODULE_0__ = __webpack_require__(/*! @jupyter-widgets/html-manager */ \"@jupyter-widgets/html-manager\");\n/* harmony import */ var _jupyter_widgets_html_manager__WEBPACK_IMPORTED_MODULE_0___default = /*#__PURE__*/__webpack_require__.n(_jupyter_widgets_html_manager__WEBPACK_IMPORTED_MODULE_0__);\n/* harmony import */ var _comm__WEBPACK_IMPORTED_MODULE_1__ = __webpack_require__(/*! ./comm */ \"./src/comm.ts\");\n/* harmony import */ var _utils__WEBPACK_IMPORTED_MODULE_2__ = __webpack_require__(/*! ./utils */ \"./src/utils.ts\");\nvar _a;\n\n\n\n/******************************************************************************\n * Define a custom HTMLManager for use with Shiny\n ******************************************************************************/\nclass OutputManager extends _jupyter_widgets_html_manager__WEBPACK_IMPORTED_MODULE_0__.HTMLManager {\n    // In a soon-to-be-released version of @jupyter-widgets/html-manager,\n    // display_view()'s first \"dummy\" argument will be removed... this shim simply\n    // makes it so that our manager can work with either version\n    // https://github.com/jupyter-widgets/ipywidgets/commit/159bbe4#diff-45c126b24c3c43d2cee5313364805c025e911c4721d45ff8a68356a215bfb6c8R42-R43\n    async display_view(view, options) {\n        const n_args = super.display_view.length;\n        if (n_args === 3) {\n            return super.display_view({}, view, options);\n        }\n        else {\n            // @ts-ignore\n            return super.display_view(view, options);\n        }\n    }\n}\n// Define our own custom module loader for Shiny\nconst shinyRequireLoader = async function (moduleName, moduleVersion) {\n    // shiny provides require.js and also sets `define.amd=false` to prevent <script>s\n    // with UMD loaders from triggering anonymous define() errors. shinywidgets should\n    // generally be able to avoid anonymous define errors though since there should only\n    // be one 'main' anonymous define() for the widget's module (located in a JS file that\n    // we've already require.config({paths: {...}})ed; and in that case, requirejs adds a\n    // data-requiremodule attribute to the <script> tag that shiny's custom define will\n    // recognize and use as the name).)\n    const oldAmd = window.define.amd;\n    // The is the original value for define.amd that require.js sets\n    window.define.amd = { jQuery: true };\n    // Store jQuery global since loading we load a module, it may overwrite it\n    // (qgrid is one good example)\n    const old$ = window.$;\n    const oldJQ = window.jQuery;\n    if (moduleName === 'qgrid') {\n        // qgrid wants to use base/js/dialog (if it's available) for full-screen tables\n        // https://github.com/quantopian/qgrid/blob/877b420/js/src/qgrid.widget.js#L11-L16\n        // Maybe that's worth supporting someday, but for now, we define it to be nothing\n        // to avoid require('qgrid') from producing an error\n        window.define(\"base/js/dialog\", [], function () { return null; });\n    }\n    return (0,_jupyter_widgets_html_manager__WEBPACK_IMPORTED_MODULE_0__.requireLoader)(moduleName, moduleVersion).finally(() => {\n        window.define.amd = oldAmd;\n        window.$ = old$;\n        window.jQuery = oldJQ;\n    });\n};\nconst manager = new OutputManager({ loader: shinyRequireLoader });\n/******************************************************************************\n* Define the Shiny binding\n******************************************************************************/\n// Ideally we'd extend Shiny's HTMLOutputBinding, but the implementation isn't exported\nclass IPyWidgetOutput extends Shiny.OutputBinding {\n    find(scope) {\n        return $(scope).find(\".shiny-ipywidget-output\");\n    }\n    onValueError(el, err) {\n        Shiny.unbindAll(el);\n        this.renderError(el, err);\n    }\n    async renderValue(el, data) {\n        // Allow for a None/null value to hide the widget (css inspired by htmlwidgets)\n        if (!data) {\n            el.style.visibility = \"hidden\";\n            return;\n        }\n        else {\n            el.style.visibility = \"inherit\";\n        }\n        // Only forward the potential to fill if `output_widget(fillable=True)`\n        // _and_ the widget instance wants to fill\n        const fill = data.fill && el.classList.contains(\"html-fill-container\");\n        if (fill)\n            el.classList.add(\"forward-fill-potential\");\n        // At this time point, we should've already handled an 'open' message, and so\n        // the model should be ready to use\n        const model = await manager.get_model(data.model_id);\n        if (!model) {\n            throw new Error(`No model found for id ${data.model_id}`);\n        }\n        const view = await manager.create_view(model, {});\n        await manager.display_view(view, { el: el });\n        // Don't allow more than one .lmWidget container, which can happen\n        // when the view is displayed more than once\n        // TODO: It's probably better to get view(s) from m.views and .remove() them\n        while (el.childNodes.length > 1) {\n            el.removeChild(el.childNodes[0]);\n        }\n        // The ipywidgets container (.lmWidget)\n        const lmWidget = el.children[0];\n        this._maybeResize(lmWidget);\n    }\n    _maybeResize(lmWidget) {\n        if (this._hasImplementation(lmWidget)) {\n            return this._doResize();\n        }\n        // Some widget implementation (e.g., ipyleaflet, pydeck) won't actually\n        // have rendered to the DOM at this point, so wait until they do\n        const mo = new MutationObserver((mutations) => {\n            if (this._hasImplementation(lmWidget)) {\n                mo.disconnect();\n                this._doResize();\n            }\n        });\n        mo.observe(lmWidget, { childList: true });\n    }\n    _doResize() {\n        // Trigger resize event to force layout (setTimeout() is needed for altair)\n        // TODO: debounce this call?\n        setTimeout(() => {\n            window.dispatchEvent(new Event('resize'));\n        }, 0);\n    }\n    _hasImplementation(lmWidget) {\n        const impl = lmWidget.children[0];\n        return impl && impl.children.length > 0;\n    }\n}\nShiny.outputBindings.register(new IPyWidgetOutput(), \"shiny.IPyWidgetOutput\");\n// Due to the way HTMLManager (and widget implementations) get loaded (via\n// require.js), the binding registration above can happen _after_ Shiny has\n// already bound the DOM, especially in the dynamic UI case (i.e., output_binding()'s\n// dependencies don't come in until after initial page load). And, in the dynamic UI\n// case, UI is rendered asychronously via Shiny.shinyapp.taskQueue, so if it exists,\n// we probably need to re-bind the DOM after the taskQueue is done.\nconst taskQueue = (_a = Shiny === null || Shiny === void 0 ? void 0 : Shiny.shinyapp) === null || _a === void 0 ? void 0 : _a.taskQueue;\nif (taskQueue) {\n    taskQueue.enqueue(() => Shiny.bindAll(document.body));\n}\n/******************************************************************************\n* Handle messages from the server-side Widget\n******************************************************************************/\n// Initialize the comm and model when a new widget is created\n// This is basically our version of https://github.com/jupyterlab/jupyterlab/blob/d33de15/packages/services/src/kernel/default.ts#L1144-L1176\nShiny.addCustomMessageHandler(\"shinywidgets_comm_open\", (msg_txt) => {\n    setBaseURL();\n    const msg = (0,_utils__WEBPACK_IMPORTED_MODULE_2__.jsonParse)(msg_txt);\n    Shiny.renderDependencies(msg.content.html_deps);\n    const comm = new _comm__WEBPACK_IMPORTED_MODULE_1__.ShinyComm(msg.content.comm_id);\n    manager.handle_comm_open(comm, msg);\n});\n// Handle any mutation of the model (e.g., add a marker to a map, without a full redraw)\n// Basically out version of https://github.com/jupyterlab/jupyterlab/blob/d33de15/packages/services/src/kernel/default.ts#L1200-L1215\nShiny.addCustomMessageHandler(\"shinywidgets_comm_msg\", (msg_txt) => {\n    const msg = (0,_utils__WEBPACK_IMPORTED_MODULE_2__.jsonParse)(msg_txt);\n    manager.get_model(msg.content.comm_id).then(m => {\n        // @ts-ignore for some reason IClassicComm doesn't have this method, but we do\n        m.comm.handle_msg(msg);\n    });\n});\n// TODO: test that this actually works\nShiny.addCustomMessageHandler(\"shinywidgets_comm_close\", (msg_txt) => {\n    const msg = (0,_utils__WEBPACK_IMPORTED_MODULE_2__.jsonParse)(msg_txt);\n    manager.get_model(msg.content.comm_id).then(m => {\n        // @ts-ignore for some reason IClassicComm doesn't have this method, but we do\n        m.comm.handle_close(msg);\n    });\n});\n// Our version of https://github.com/jupyter-widgets/widget-cookiecutter/blob/9694718/%7B%7Bcookiecutter.github_project_name%7D%7D/js/lib/extension.js#L8\nfunction setBaseURL(x = '') {\n    const base_url = document.querySelector('body').getAttribute('data-base-url');\n    if (!base_url) {\n        document.querySelector('body').setAttribute('data-base-url', x);\n    }\n}\n\n\n//# sourceURL=webpack://@jupyter-widgets/shiny-embed-manager/./src/output.ts?");
 
 /***/ }),