diff --git a/js/ui/contactDisplay.js b/js/ui/contactDisplay.js
index 390bd23ed..6cbc59824 100644
--- a/js/ui/contactDisplay.js
+++ b/js/ui/contactDisplay.js
@@ -63,7 +63,7 @@ const Contact = new Lang.Class({
                         this.individual.full_name ||
                         this.individual.nickname  ||
                         email                     ||
-                        _("Unknown");
+                        C_("contact", "Unknown");
         let aliasLabel = new St.Label({ text: aliasText,
                                         style_class: 'contact-details-alias' });
         details.add(aliasLabel, { x_fill: true,
diff --git a/js/ui/notificationDaemon.js b/js/ui/notificationDaemon.js
index cf89733f8..a02898a6f 100644
--- a/js/ui/notificationDaemon.js
+++ b/js/ui/notificationDaemon.js
@@ -483,7 +483,7 @@ const NotificationDaemon = new Lang.Class({
     },
 
     _onTrayIconAdded: function(o, icon) {
-        let source = this._getSource(icon.title || icon.wm_class || _("Unknown"), icon.pid, null, null, icon);
+        let source = this._getSource(icon.title || icon.wm_class || C_("program", "Unknown"), icon.pid, null, null, icon);
     },
 
     _onTrayIconRemoved: function(o, icon) {
diff --git a/js/ui/status/power.js b/js/ui/status/power.js
index 84f6b2da7..978d009b9 100644
--- a/js/ui/status/power.js
+++ b/js/ui/status/power.js
@@ -212,7 +212,7 @@ const DeviceItem = new Lang.Class({
         case UPDeviceType.COMPUTER:
             return _("Computer");
         default:
-            return _("Unknown");
+            return C_("device", "Unknown");
         }
     }
 });
diff --git a/src/shell-app.c b/src/shell-app.c
index 31756a329..d452fd303 100644
--- a/src/shell-app.c
+++ b/src/shell-app.c
@@ -371,7 +371,7 @@ shell_app_get_name (ShellApp *app)
 
       name = meta_window_get_wm_class (window);
       if (!name)
-        name = _("Unknown");
+        name = C_("program", "Unknown");
       return name;
     }
 }