diff --git a/src/apps.js b/src/apps.js
index 6ad34c518..2c2ecb78e 100644
--- a/src/apps.js
+++ b/src/apps.js
@@ -1400,24 +1400,32 @@ function repair(appId, data, auditSource, callback) {
 
         const appError = app.error || {}; // repair can always be called
         const newState = appError.installationState ? appError.installationState : exports.ISTATE_PENDING_CONFIGURE;
+
         debug(`Repairing app with error: ${JSON.stringify(error)} and state: ${newState}`);
 
-        let values = _.pick(data, 'location', 'domain', 'alternateDomains'); // FIXME: validate
+        let values = _.pick(data, 'location', 'domain', 'alternateDomains');
 
-        tasks.get(appError.taskId || '', function (error, task) {
-            let args = !error ? task.args[1] : {}; // the first argument is the app id
-            if ('backupId' in data) {
-                args.restoreConfig = data.backupId ? { backupId: data.backupId, backupFormat: data.backupFormat, oldManifest: app.manifest } : null; // when null, apptask simply reinstalls
-            }
-            if ('overwriteDns' in data) args.overwriteDns = data.overwriteDns;
+        const locations = (values.location ? [ { subdomain: values.location, domain: values.domain } ] : []).concat(values.alternateDomains || []);
+        validateLocations(locations, function (error, domainObjectMap) {
+            if (error) return callback(error);
 
-            // create a new task instead of updating the old one, since it helps tracking
-            addTask(appId, newState, { args, values, requiredState: null }, function (error, result) {
-                if (error) return callback(error);
+            tasks.get(appError.taskId || '', function (error, task) {
+                let args = !error ? task.args[1] : {}; // pick args for the failed task. the first argument is the app id
 
-                eventlog.add(eventlog.ACTION_APP_REPAIR, auditSource, { taskId: result.taskId, app, newState });
+                if ('backupId' in data) {
+                    args.restoreConfig = data.backupId ? { backupId: data.backupId, backupFormat: data.backupFormat, oldManifest: app.manifest } : null; // when null, apptask simply reinstalls
+                }
+                args.overwriteDns = 'overwriteDns' in data ? data.overwriteDns : false;
 
-                callback(null, { taskId: result.taskId });
+                // create a new task instead of updating the old one, since it helps tracking
+                addTask(appId, newState, { args, values, requiredState: null }, function (error, result) {
+                    if (error && error.reason === AppsError.ALREADY_EXISTS) error = getDuplicateErrorDetails(error.message, locations, domainObjectMap, { /* portBindings */});
+                    if (error) return callback(error);
+
+                    eventlog.add(eventlog.ACTION_APP_REPAIR, auditSource, { taskId: result.taskId, app, newState });
+
+                    callback(null, { taskId: result.taskId });
+                });
             });
         });
     });