diff --git a/src/org/fdroid/fdroid/AppDetails.java b/src/org/fdroid/fdroid/AppDetails.java
index 2e8f49867..9f5eb2d14 100644
--- a/src/org/fdroid/fdroid/AppDetails.java
+++ b/src/org/fdroid/fdroid/AppDetails.java
@@ -913,6 +913,7 @@ public class AppDetails extends ListActivity {
         Intent intent = new Intent(Intent.ACTION_VIEW);
         intent.setDataAndType(Uri.parse("file://" + file.getPath()),
                 "application/vnd.android.package-archive");
+        intent.putExtra(Intent.EXTRA_NOT_UNKNOWN_SOURCE, true);
         startActivityForResult(intent, REQUEST_INSTALL);
         ((FDroidApp) getApplication()).invalidateApp(id);
     }