diff --git a/src/core/login/lang/en.json b/src/core/login/lang/en.json
index faf05a97a..c9031b28d 100644
--- a/src/core/login/lang/en.json
+++ b/src/core/login/lang/en.json
@@ -32,6 +32,7 @@
     "invalidurl": "Invalid URL specified",
     "invalidvaluemax": "The maximum value is {{$a}}",
     "invalidvaluemin": "The minimum value is {{$a}}",
+    "legacymoodleversion": "You are trying to connect to an unsupported Moodle version. Please, download the Moodle Classic app to access this Moodle site.",
     "localmobileunexpectedresponse": "Moodle Mobile Additional Features check returned an unexpected response, you will be authenticated using the standard Mobile service.",
     "login": "Log in",
     "loginbutton": "Log in",
diff --git a/src/core/login/pages/reconnect/reconnect.ts b/src/core/login/pages/reconnect/reconnect.ts
index 99e1ad423..27c853129 100644
--- a/src/core/login/pages/reconnect/reconnect.ts
+++ b/src/core/login/pages/reconnect/reconnect.ts
@@ -137,7 +137,7 @@ export class CoreLoginReconnectPage {
         this.sitesProvider.getUserToken(siteUrl, username, password).then((data) => {
             return this.sitesProvider.updateSiteToken(this.infoSiteUrl, username, data.token, data.privateToken).then(() => {
                 // Update site info too because functions might have changed (e.g. unisntall local_mobile).
-                return this.sitesProvider.updateSiteInfoByUrl(this.infoSiteUrl, username).finally(() => {
+                return this.sitesProvider.updateSiteInfoByUrl(this.infoSiteUrl, username).then(() => {
                     // Reset fields so the data is not in the view anymore.
                     this.credForm.controls['password'].reset();
 
@@ -148,8 +148,8 @@ export class CoreLoginReconnectPage {
                         return this.loginHelper.goToSiteInitialPage();
                     }
                 }).catch((error) => {
-                    // Site deleted? Go back to login page.
-                    this.domUtils.showErrorModal('core.login.errorupdatesite', true);
+                    // Error, go back to login page.
+                    this.domUtils.showErrorModalDefault(error, 'core.login.errorupdatesite', true);
                     this.cancel();
                 });
             });
diff --git a/src/core/login/providers/helper.ts b/src/core/login/providers/helper.ts
index 942fb37da..ef2460cb0 100644
--- a/src/core/login/providers/helper.ts
+++ b/src/core/login/providers/helper.ts
@@ -178,8 +178,10 @@ export class CoreLoginHelperProvider {
                 this.goToSiteInitialPage();
             }
         }).catch((errorMessage) => {
-            if (typeof errorMessage == 'string' && errorMessage != '') {
+            if (errorMessage) {
+                // An error occurred, display the error and logout the user.
                 this.domUtils.showErrorModal(errorMessage);
+                this.sitesProvider.logout();
             }
         }).finally(() => {
             modal.dismiss();
@@ -436,8 +438,8 @@ export class CoreLoginHelperProvider {
             const info = this.sitesProvider.getCurrentSite().getInfo();
             if (typeof info != 'undefined' && typeof info.username != 'undefined') {
                 return this.sitesProvider.updateSiteToken(info.siteurl, info.username, token, privateToken).then(() => {
-                    this.sitesProvider.updateSiteInfoByUrl(info.siteurl, info.username);
-                }).catch(() => {
+                    return this.sitesProvider.updateSiteInfoByUrl(info.siteurl, info.username);
+                }, () => {
                     // Error updating token, return proper error message.
                     return Promise.reject(this.translate.instant('core.login.errorupdatesite'));
                 });
diff --git a/src/providers/sites.ts b/src/providers/sites.ts
index 2c087c955..c3e8678bb 100644
--- a/src/providers/sites.ts
+++ b/src/providers/sites.ts
@@ -1050,6 +1050,11 @@ export class CoreSitesProvider {
             return site.fetchSiteInfo().then((info) => {
                 site.setInfo(info);
 
+                if (this.isLegacyMoodleByInfo(info)) {
+                    // The Moodle version is not supported, reject.
+                    return Promise.reject(this.translate.instant('core.login.legacymoodleversion'));
+                }
+
                 // Try to get the site config.
                 return this.getSiteConfig(site).catch(() => {
                     // Error getting config, keep the current one.
@@ -1227,4 +1232,14 @@ export class CoreSitesProvider {
 
         return site && site.wsAvailable(method, checkPrefix);
     }
+
+    /**
+     * Check if a site is a legacy site by its info.
+     *
+     * @param {any} info The site info.
+     * @return {boolean} Whether it's a legacy Moodle.
+     */
+    isLegacyMoodleByInfo(info: any): boolean {
+        return this.isValidMoodleVersion(info) == this.LEGACY_APP_VERSION;
+    }
 }
diff --git a/src/providers/update-manager.ts b/src/providers/update-manager.ts
index 744adcd5b..fb451a9f9 100644
--- a/src/providers/update-manager.ts
+++ b/src/providers/update-manager.ts
@@ -367,6 +367,10 @@ export class CoreUpdateManagerProvider implements CoreInitHandler {
             // In version 2018 we adapted the forum offline stores to match a new schema.
             // However, due to the migration of data to SQLite we can no longer do that.
 
+            if (versionCode >= 3500 && versionApplied < 3500 && versionApplied > 0) {
+                promises.push(this.logoutLegacySites());
+            }
+
             return Promise.all(promises).then(() => {
                 return this.configProvider.set(this.VERSION_APPLIED, versionCode);
             }).catch((error) => {
@@ -684,4 +688,26 @@ export class CoreUpdateManagerProvider implements CoreInitHandler {
             });
         });
     }
+
+    /**
+     * Logout from legacy sites.
+     *
+     * @return {Promise<any>} Promise resolved when done.
+     */
+    protected logoutLegacySites(): Promise<any> {
+        return this.sitesProvider.getSitesIds().then((siteIds) => {
+            const promises = [];
+
+            siteIds.forEach((siteId) => {
+                promises.push(this.sitesProvider.getSite(siteId).then((site) => {
+                    // If the site is a legacy site, mark it as logged out so the user has to authenticate again.
+                    if (this.sitesProvider.isLegacyMoodleByInfo(site.getInfo())) {
+                        return this.sitesProvider.setSiteLoggedOut(site.getId(), true);
+                    }
+                }));
+            });
+
+            return this.utils.allPromises(promises);
+        });
+    }
 }