diff --git a/src/IdentityAuthClient.js b/src/IdentityAuthClient.js
index 755205d5e2..12c0c5b147 100644
--- a/src/IdentityAuthClient.js
+++ b/src/IdentityAuthClient.js
@@ -14,15 +14,50 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { SERVICE_TYPES } from 'matrix-js-sdk';
+import Matrix, { SERVICE_TYPES } from 'matrix-js-sdk';
 
 import MatrixClientPeg from './MatrixClientPeg';
 import { Service, startTermsFlow, TermsNotSignedError } from './Terms';
 
 export default class IdentityAuthClient {
-    constructor() {
+    /**
+     * Creates a new identity auth client
+     * @param {string} identityUrl The URL to contact the identity server with.
+     * When provided, this class will operate solely within memory, refusing to
+     * persist any information such as tokens. Default null (not provided).
+     */
+    constructor(identityUrl = null) {
         this.accessToken = null;
         this.authEnabled = true;
+
+        if (identityUrl) {
+            // XXX: We shouldn't have to create a whole new MatrixClient just to
+            // do identity server auth. The functions don't take an identity URL
+            // though, and making all of them take one could lead to developer
+            // confusion about what the idBaseUrl does on a client. Therefore, we
+            // just make a new client and live with it.
+            this.tempClient = Matrix.createClient({
+                baseUrl: "", // invalid by design
+                idBaseUrl: identityUrl,
+            });
+        } else {
+            // Indicates that we're using the real client, not some workaround.
+            this.tempClient = null;
+        }
+    }
+
+    get _matrixClient() {
+        return this.tempClient ? this.tempClient : MatrixClientPeg.get();
+    }
+
+    _writeToken() {
+        if (this.tempClient) return; // temporary client: ignore
+        window.localStorage.setItem("mx_is_access_token", token);
+    }
+
+    _readToken() {
+        if (this.tempClient) return null; // temporary client: ignore
+        return window.localStorage.getItem("mx_is_access_token");
     }
 
     hasCredentials() {
@@ -38,14 +73,14 @@ export default class IdentityAuthClient {
 
         let token = this.accessToken;
         if (!token) {
-            token = window.localStorage.getItem("mx_is_access_token");
+            token = this._readToken();
         }
 
         if (!token) {
             token = await this.registerForToken();
             if (token) {
                 this.accessToken = token;
-                window.localStorage.setItem("mx_is_access_token", token);
+                this._writeToken();
             }
             return token;
         }
@@ -61,7 +96,7 @@ export default class IdentityAuthClient {
             token = await this.registerForToken();
             if (token) {
                 this.accessToken = token;
-                window.localStorage.setItem("mx_is_access_token", token);
+                this._writeToken();
             }
         }
 
@@ -70,13 +105,13 @@ export default class IdentityAuthClient {
 
     async _checkToken(token) {
         try {
-            await MatrixClientPeg.get().getIdentityAccount(token);
+            await this._matrixClient.getIdentityAccount(token);
         } catch (e) {
             if (e.errcode === "M_TERMS_NOT_SIGNED") {
                 console.log("Identity Server requires new terms to be agreed to");
                 await startTermsFlow([new Service(
                     SERVICE_TYPES.IS,
-                    MatrixClientPeg.get().idBaseUrl,
+                    this._matrixClient.getIdentityServerUrl(),
                     token,
                 )]);
                 return;
@@ -95,7 +130,7 @@ export default class IdentityAuthClient {
         try {
             const hsOpenIdToken = await MatrixClientPeg.get().getOpenIdToken();
             const { access_token: identityAccessToken } =
-                await MatrixClientPeg.get().registerWithIdentityServer(hsOpenIdToken);
+                await this._matrixClient.registerWithIdentityServer(hsOpenIdToken);
             await this._checkToken(identityAccessToken);
             return identityAccessToken;
         } catch (e) {
diff --git a/src/components/views/settings/SetIdServer.js b/src/components/views/settings/SetIdServer.js
index 398e578e8d..c4842d2ae9 100644
--- a/src/components/views/settings/SetIdServer.js
+++ b/src/components/views/settings/SetIdServer.js
@@ -22,6 +22,8 @@ import MatrixClientPeg from "../../../MatrixClientPeg";
 import SdkConfig from "../../../SdkConfig";
 import Modal from '../../../Modal';
 import dis from "../../../dispatcher";
+import IdentityAuthClient from "../../../IdentityAuthClient";
+import {SERVICE_TYPES} from "matrix-js-sdk";
 
 /**
  * If a url has no path component, etc. abbreviate it to just the hostname
@@ -98,6 +100,7 @@ export default class SetIdServer extends React.Component {
             idServer: defaultIdServer,
             error: null,
             busy: false,
+            checking: false,
         };
     }
 
@@ -108,14 +111,14 @@ export default class SetIdServer extends React.Component {
     };
 
     _getTooltip = () => {
-        if (this.state.busy) {
+        if (this.state.checking) {
             const InlineSpinner = sdk.getComponent('views.elements.InlineSpinner');
             return <div>
                 <InlineSpinner />
                 { _t("Checking server") }
             </div>;
         } else if (this.state.error) {
-            return this.state.error;
+            return <span className='warning'>{this.state.error}</span>;
         } else {
             return null;
         }
@@ -125,25 +128,67 @@ export default class SetIdServer extends React.Component {
         return !!this.state.idServer && !this.state.busy;
     };
 
+    _continueTerms = (fullUrl) => {
+        MatrixClientPeg.get().setIdentityServerUrl(fullUrl);
+        localStorage.removeItem("mx_is_access_token");
+        localStorage.setItem("mx_is_url", fullUrl);
+        dis.dispatch({action: 'id_server_changed'});
+        this.setState({idServer: '', busy: false, error: null});
+    };
+
     _saveIdServer = async (e) => {
         e.preventDefault();
 
-        this.setState({busy: true});
+        this.setState({busy: true, checking: true, error: null});
 
         const fullUrl = unabbreviateUrl(this.state.idServer);
 
-        const errStr = await checkIdentityServerUrl(fullUrl);
+        let errStr = await checkIdentityServerUrl(fullUrl);
 
         let newFormValue = this.state.idServer;
         if (!errStr) {
-            MatrixClientPeg.get().setIdentityServerUrl(fullUrl);
-            localStorage.removeItem("mx_is_access_token");
-            localStorage.setItem("mx_is_url", fullUrl);
-            dis.dispatch({action: 'id_server_changed'});
-            newFormValue = '';
+            try {
+                this.setState({checking: false}); // clear tooltip
+
+                // Test the identity server by trying to register with it. This
+                // may result in a terms of service prompt.
+                const authClient = new IdentityAuthClient(fullUrl);
+                await authClient.getAccessToken();
+
+                // Double check that the identity server even has terms of service.
+                const terms = await MatrixClientPeg.get().getTerms(SERVICE_TYPES.IS, fullUrl);
+                if (!terms || !terms["policies"] || Object.keys(terms["policies"]).length <= 0) {
+                    const QuestionDialog = sdk.getComponent("views.dialogs.QuestionDialog");
+                    Modal.createTrackedDialog('No Terms Warning', '', QuestionDialog, {
+                        title: _t("Identity server has no terms of service"),
+                        description: (
+                            <div>
+                                <span className="warning">
+                                    {_t("The identity server you have chosen does not have any terms of service.")}
+                                </span>
+                                <span>
+                                    &nbsp;{_t("Only continue if you trust the owner of the server.")}
+                                </span>
+                            </div>
+                        ),
+                        button: _t("Continue"),
+                        onFinished: async (confirmed) => {
+                            if (!confirmed) return;
+                            this._continueTerms(fullUrl);
+                        },
+                    });
+                    return;
+                }
+
+                this._continueTerms(fullUrl);
+            } catch (e) {
+                console.error(e);
+                errStr = _t("Terms of service not accepted or the identity server is invalid.");
+            }
         }
         this.setState({
             busy: false,
+            checking: false,
             error: errStr,
             currentClientIdServer: MatrixClientPeg.get().getIdentityServerUrl(),
             idServer: newFormValue,
diff --git a/src/i18n/strings/en_EN.json b/src/i18n/strings/en_EN.json
index b982644516..09337fc7fc 100644
--- a/src/i18n/strings/en_EN.json
+++ b/src/i18n/strings/en_EN.json
@@ -548,6 +548,10 @@
     "Not a valid Identity Server (status code %(code)s)": "Not a valid Identity Server (status code %(code)s)",
     "Could not connect to Identity Server": "Could not connect to Identity Server",
     "Checking server": "Checking server",
+    "Identity server has no terms of service": "Identity server has no terms of service",
+    "The identity server you have chosen does not have any terms of service.": "The identity server you have chosen does not have any terms of service.",
+    "Only continue if you trust the owner of the server.": "Only continue if you trust the owner of the server.",
+    "Terms of service not accepted or the identity server is invalid.": "Terms of service not accepted or the identity server is invalid.",
     "Disconnect Identity Server": "Disconnect Identity Server",
     "Disconnect from the identity server <idserver />?": "Disconnect from the identity server <idserver />?",
     "Disconnect": "Disconnect",
@@ -562,7 +566,6 @@
     "Terms of service not accepted or the integration manager is invalid.": "Terms of service not accepted or the integration manager is invalid.",
     "Integration manager has no terms of service": "Integration manager has no terms of service",
     "The integration manager you have chosen does not have any terms of service.": "The integration manager you have chosen does not have any terms of service.",
-    "Only continue if you trust the owner of the server.": "Only continue if you trust the owner of the server.",
     "You are currently using <b>%(serverName)s</b> to manage your bots, widgets, and sticker packs.": "You are currently using <b>%(serverName)s</b> to manage your bots, widgets, and sticker packs.",
     "Add which integration manager you want to manage your bots, widgets, and sticker packs.": "Add which integration manager you want to manage your bots, widgets, and sticker packs.",
     "Integration Manager": "Integration Manager",