diff --git a/app/error-handler.js b/app/error-handler.js
new file mode 100644
index 00000000..30f77068
--- /dev/null
+++ b/app/error-handler.js
@@ -0,0 +1,61 @@
+// NB: this should *not* be included as a module until we have
+// native support in the browsers, so that our error handler
+// can catch script-loading errors.
+
+
+(function(){
+    "use strict";
+
+    function convertNewlines(msg, parentElem) {
+        const lines = msg.split("\n");
+        lines.forEach(function (line) {
+            parentElem.appendChild(document.createElement("br"));
+            parentElem.appendChild(document.createTextNode(line));
+        });
+        parentElem.removeChild(parentElem.firstChild);
+        return parentElem;
+    }
+
+    // Fallback for all uncought errors
+    function handleError (event, err) {
+        try {
+            const msg = document.getElementById('noVNC_fallback_errormsg');
+
+            // Only show the initial error
+            if (msg.hasChildNodes()) {
+                return false;
+            }
+
+            var div = document.createElement("div");
+            div.classList.add('noVNC_message');
+            convertNewlines(event.message, div);
+            msg.appendChild(div);
+
+            if (event.filename !== undefined && event.lineno !== undefined && event.colno !== undefined) {
+                div = document.createElement("div");
+                div.className = 'noVNC_location';
+                    const text = event.filename + ":" + event.lineno + ":" + event.colno;
+                    div.appendChild(document.createTextNode(text));
+                msg.appendChild(div);
+            }
+
+            if ((err !== undefined) &&
+                (err.stack !== undefined)) {
+                div = document.createElement("div");
+                div.className = 'noVNC_stack';
+                div.appendChild(document.createTextNode(err.stack));
+                msg.appendChild(div);
+            }
+
+            document.getElementById('noVNC_fallback_error')
+                .classList.add("noVNC_open");
+        } catch (exc) {
+            document.write("noVNC encountered an error.");
+        }
+        // Don't return true since this would prevent the error
+        // from being printed to the browser console.
+        return false;
+    }
+    window.addEventListener('error', function (evt) { handleError(evt, evt.error); });
+    window.addEventListener('unhandledrejection', function (evt) { handleError(evt.reason, evt.reason); });
+})();
diff --git a/app/styles/base.css b/app/styles/base.css
index 4cec1735..30146963 100644
--- a/app/styles/base.css
+++ b/app/styles/base.css
@@ -247,6 +247,11 @@ select:active {
   font-weight: normal;
 }
 
+#noVNC_fallback_errormsg .noVNC_message {
+  display: inline-block;
+  text-align: left;
+}
+
 #noVNC_fallback_error .noVNC_location {
   font-style: italic;
   font-size: 0.8em;
diff --git a/app/ui.js b/app/ui.js
index d59204c8..46826221 100644
--- a/app/ui.js
+++ b/app/ui.js
@@ -21,46 +21,6 @@ import RFB from "../core/rfb.js";
 import Display from "../core/display.js";
 import * as WebUtil from "./webutil.js";
 
-// Fallback for all uncought errors
-window.addEventListener('error', function(event) {
-    try {
-        var msg, div, text;
-
-        msg = document.getElementById('noVNC_fallback_errormsg');
-
-        // Only show the initial error
-        if (msg.hasChildNodes()) {
-            return false;
-        }
-
-        div = document.createElement("div");
-        div.appendChild(document.createTextNode(event.message));
-        msg.appendChild(div);
-
-        div = document.createElement("div");
-        div.className = 'noVNC_location';
-        text = event.filename + ":" + event.lineno + ":" + event.colno;
-        div.appendChild(document.createTextNode(text));
-        msg.appendChild(div);
-
-        if ((event.error !== undefined) &&
-            (event.error.stack !== undefined)) {
-            div = document.createElement("div");
-            div.className = 'noVNC_stack';
-            div.appendChild(document.createTextNode(event.error.stack));
-            msg.appendChild(div);
-        }
-
-        document.getElementById('noVNC_fallback_error')
-            .classList.add("noVNC_open");
-    } catch (exc) {
-        document.write("noVNC encountered an error.");
-    }
-    // Don't return true since this would prevent the error
-    // from being printed to the browser console.
-    return false;
-});
-
 const UI = {
 
     connected: false,
@@ -1751,11 +1711,10 @@ if (l10n.language !== "en" && l10n.dictionary === undefined) {
         // wait for translations to load before loading the UI
         UI.prime();
     }, function (err) {
-        throw err; 
+        throw err;
     });
 } else {
     UI.prime();
 }
 
-
 export default UI;
diff --git a/utils/use_require.js b/utils/use_require.js
index bfa14f6f..f0383d09 100755
--- a/utils/use_require.js
+++ b/utils/use_require.js
@@ -21,6 +21,17 @@ var vendor_path = path.resolve(__dirname, '..', 'vendor');
 var out_dir_base = path.resolve(__dirname, '..', 'build');
 var lib_dir_base = path.resolve(__dirname, '..', 'lib');
 
+const no_copy_files = new Set([
+    // skip these -- they don't belong in the processed application
+    path.join(vendor_path, 'sinon.js'),
+    path.join(vendor_path, 'browser-es-module-loader'),
+]);
+
+const no_transform_files = new Set([
+    // don't transform this -- we want it imported as-is to properly catch loading errors
+    path.join(app_path, 'error-handler.js'),
+]);
+
 // walkDir *recursively* walks directories trees,
 // calling the callback for all normal files found.
 var walkDir = function (base_path, cb, filter) {
@@ -93,6 +104,8 @@ var make_lib_files = function (import_format, source_maps, with_app_dir) {
     const helper = helpers[import_format];
     
     var handleDir = (js_only, in_path_base, filename) => {
+        if (no_copy_files.has(filename)) return;
+
         const out_path = path.join(out_path_base, path.relative(in_path_base, filename));
         if(path.extname(filename) !== '.js') {
             if (!js_only) {
@@ -103,10 +116,17 @@ var make_lib_files = function (import_format, source_maps, with_app_dir) {
         }
 
         fse.ensureDir(path.dirname(out_path), () => {
+            if (no_transform_files.has(filename)) {
+                console.log(`Writing ${out_path}`);
+                fse.copy(filename, out_path, (err) => { if (err) throw err; });
+                return;
+            }
+
             const opts = babel_opts();
             if (helper && helpers.optionsOverride) {
                 helper.optionsOverride(opts);
             }
+
             babel.transformFile(filename, babel_opts(), (err, res) => {
                 console.log(`Writing ${out_path}`);
                 if (err) throw err;
@@ -124,11 +144,11 @@ var make_lib_files = function (import_format, source_maps, with_app_dir) {
         });
     };
 
-    walkDir(core_path, handleDir.bind(null, true, in_path || core_path));
-    walkDir(vendor_path, handleDir.bind(null, true, in_path || main_path), (filepath, stats) => !((stats.isDirectory() && path.basename(filepath) === 'browser-es-module-loader') || path.basename(filepath) === 'sinon.js'));
+    walkDir(core_path, handleDir.bind(null, true, in_path || core_path), (filename, stats) => !no_copy_files.has(filename));
+    walkDir(vendor_path, handleDir.bind(null, true, in_path || main_path), (filename, stats) => !no_copy_files.has(filename));
 
     if (with_app_dir) {
-        walkDir(app_path, handleDir.bind(null, false, in_path || app_path));
+        walkDir(app_path, handleDir.bind(null, false, in_path || app_path), (filename, stats) => !no_copy_files.has(filename));
 
         const out_app_path = path.join(out_path_base, 'app.js');
         if (helper && helper.appWriter) {
diff --git a/vendor/browser-es-module-loader/dist/browser-es-module-loader.js b/vendor/browser-es-module-loader/dist/browser-es-module-loader.js
index 3d123da6..0d22bab2 100644
--- a/vendor/browser-es-module-loader/dist/browser-es-module-loader.js
+++ b/vendor/browser-es-module-loader/dist/browser-es-module-loader.js
@@ -1180,7 +1180,22 @@ if (typeof document != 'undefined' && document.getElementsByTagName) {
       if (script.type == 'module' && !script.loaded) {
         script.loaded = true;
         if (script.src) {
-          loader.import(script.src);
+          loader.import(script.src).catch(function(err) {
+              // dispatch an error event so that we can display in errors in browsers
+              // that don't yet support unhandledrejection
+              try {
+                  var evt = new Event('error');
+              } catch (_eventError) {
+                  var evt = document.createEvent('Event');
+                  evt.initEvent('error', true, true);
+              }
+              evt.message = err.message;
+              evt.error = err;
+              window.dispatchEvent(evt);
+
+              // throw so it still shows up in the console
+              throw err;
+          });
         }
         // anonymous modules supported via a custom naming scheme and registry
         else {
@@ -1191,7 +1206,22 @@ if (typeof document != 'undefined' && document.getElementsByTagName) {
 
           var anonName = resolveIfNotPlain(uri, baseURI);
           anonSources[anonName] = script.innerHTML;
-          loader.import(anonName);
+          loader.import(anonName).catch(function(err) {
+              // dispatch an error event so that we can display in errors in browsers
+              // that don't yet support unhandledrejection
+              try {
+                  var evt = new Event('error');
+              } catch (_eventError) {
+                  var evt = document.createEvent('Event');
+                  evt.initEvent('error', true, true);
+              }
+              evt.message = err.message;
+              evt.error = err;
+              window.dispatchEvent(evt);
+
+              // throw so it still shows up in the console
+              throw err;
+          });
         }
       }
     }
diff --git a/vendor/browser-es-module-loader/src/browser-es-module-loader.js b/vendor/browser-es-module-loader/src/browser-es-module-loader.js
index 9ba7c36e..a9d72097 100644
--- a/vendor/browser-es-module-loader/src/browser-es-module-loader.js
+++ b/vendor/browser-es-module-loader/src/browser-es-module-loader.js
@@ -20,7 +20,22 @@ if (typeof document != 'undefined' && document.getElementsByTagName) {
       if (script.type == 'module' && !script.loaded) {
         script.loaded = true;
         if (script.src) {
-          loader.import(script.src);
+          loader.import(script.src).catch(function(err) {
+              // dispatch an error event so that we can display in errors in browsers
+              // that don't yet support unhandledrejection
+              try {
+                  var evt = new Event('error');
+              } catch (_eventError) {
+                  var evt = document.createEvent('Event');
+                  evt.initEvent('error', true, true);
+              }
+              evt.message = err.message;
+              evt.error = err;
+              window.dispatchEvent(evt);
+
+              // throw so it still shows up in the console
+              throw err;
+          });
         }
         // anonymous modules supported via a custom naming scheme and registry
         else {
@@ -31,7 +46,22 @@ if (typeof document != 'undefined' && document.getElementsByTagName) {
 
           var anonName = resolveIfNotPlain(uri, baseURI);
           anonSources[anonName] = script.innerHTML;
-          loader.import(anonName);
+          loader.import(anonName).catch(function(err) {
+              // dispatch an error event so that we can display in errors in browsers
+              // that don't yet support unhandledrejection
+              try {
+                  var evt = new Event('error');
+              } catch (_eventError) {
+                  var evt = document.createEvent('Event');
+                  evt.initEvent('error', true, true);
+              }
+              evt.message = err.message;
+              evt.error = err;
+              window.dispatchEvent(evt);
+
+              // throw so it still shows up in the console
+              throw err;
+          });
         }
       }
     }
diff --git a/vnc.html b/vnc.html
index b4f43e73..10cc1430 100644
--- a/vnc.html
+++ b/vnc.html
@@ -59,6 +59,9 @@
         src='http://getfirebug.com/releases/lite/1.2/firebug-lite-compressed.js'></script>
     -->
 
+    <!-- this is included as a normal file in order to catch script-loading errors as well -->
+    <script type="text/javascript" src="app/error-handler.js"></script>
+
     <!-- begin scripts -->
     <script src="vendor/browser-es-module-loader/dist/browser-es-module-loader.js"></script>
     <script type="module" src="app/ui.js"></script>