diff --git a/clientgui/BOINCGUIApp.cpp b/clientgui/BOINCGUIApp.cpp
index f7ae21b934..b69e629b22 100644
--- a/clientgui/BOINCGUIApp.cpp
+++ b/clientgui/BOINCGUIApp.cpp
@@ -411,6 +411,7 @@ bool CBOINCGUIApp::OnInit() {
     // Detect if BOINC Manager is already running, if so, bring it into the
     // foreground and then exit.
     if (DetectDuplicateInstance()) {
+      printf( "Another instance of BOINC Manager already running.\n");
             return false;
     }