diff --git a/src/components/views/dialogs/BugReportDialog.js b/src/components/views/dialogs/BugReportDialog.js
index 6e337d53dc..9bb716fe3f 100644
--- a/src/components/views/dialogs/BugReportDialog.js
+++ b/src/components/views/dialogs/BugReportDialog.js
@@ -137,12 +137,20 @@ export default class BugReportDialog extends React.Component {
             );
         }
 
+        let warning;
+        if (window.Modernizr && Object.values(window.Modernizr).some(support => support === false)) {
+            warning = <p><b>
+                { _t("Reminder: Your browser is unsupported, so your experience may be unpredictable.") }
+            </b></p>;
+        }
+
         return (
             <BaseDialog className="mx_BugReportDialog" onFinished={this._onCancel}
                     title={_t('Submit debug logs')}
                 contentId='mx_Dialog_content'
             >
                 <div className="mx_Dialog_content" id='mx_Dialog_content'>
+                    { warning }
                     <p>
                         { _t(
                             "Debug logs contain application usage data including your " +
diff --git a/src/i18n/strings/en_EN.json b/src/i18n/strings/en_EN.json
index d00bc894e4..80d466724b 100644
--- a/src/i18n/strings/en_EN.json
+++ b/src/i18n/strings/en_EN.json
@@ -1528,6 +1528,7 @@
     "Logs sent": "Logs sent",
     "Thank you!": "Thank you!",
     "Failed to send logs: ": "Failed to send logs: ",
+    "Reminder: Your browser is unsupported, so your experience may be unpredictable.": "Reminder: Your browser is unsupported, so your experience may be unpredictable.",
     "Debug logs contain application usage data including your username, the IDs or aliases of the rooms or groups you have visited and the usernames of other users. They do not contain messages.": "Debug logs contain application usage data including your username, the IDs or aliases of the rooms or groups you have visited and the usernames of other users. They do not contain messages.",
     "Before submitting logs, you must <a>create a GitHub issue</a> to describe your problem.": "Before submitting logs, you must <a>create a GitHub issue</a> to describe your problem.",
     "GitHub issue": "GitHub issue",
diff --git a/src/rageshake/submit-rageshake.js b/src/rageshake/submit-rageshake.js
index 00ef87f89c..55c89427c5 100644
--- a/src/rageshake/submit-rageshake.js
+++ b/src/rageshake/submit-rageshake.js
@@ -96,12 +96,14 @@ export default async function sendBugReport(bugReportEndpoint, opts) {
         body.append('device_id', client.deviceId);
     }
 
-    const keys = [`ed25519:${client.getDeviceEd25519Key()}`];
-    if (client.getDeviceCurve25519Key) {
-        keys.push(`curve25519:${client.getDeviceCurve25519Key()}`);
+    if (client.isCryptoEnabled()) {
+        const keys = [`ed25519:${client.getDeviceEd25519Key()}`];
+        if (client.getDeviceCurve25519Key) {
+            keys.push(`curve25519:${client.getDeviceCurve25519Key()}`);
+        }
+        body.append('device_keys', keys.join(', '));
+        body.append('cross_signing_key', client.getCrossSigningId());
     }
-    body.append('device_keys', keys.join(', '));
-    body.append('cross_signing_key', client.getCrossSigningId());
 
     if (opts.label) {
         body.append('label', opts.label);
@@ -136,6 +138,13 @@ export default async function sendBugReport(bugReportEndpoint, opts) {
         } catch (e) {}
     }
 
+    if (window.Modernizr) {
+        const missingFeatures = Object.keys(window.Modernizr).filter(key => window.Modernizr[key] === false);
+        if (missingFeatures.length > 0) {
+            body.append("modernizr_missing_features", missingFeatures.join(", "));
+        }
+    }
+
     if (opts.sendLogs) {
         progressCallback(_t("Collecting logs"));
         const logs = await rageshake.getLogsForReport();