diff --git a/src/PrefsManager.cpp b/src/PrefsManager.cpp
index 9ea55aa8f6..24c3a43c79 100644
--- a/src/PrefsManager.cpp
+++ b/src/PrefsManager.cpp
@@ -353,7 +353,7 @@ void PrefsManager::StoreGamePrefs()
 	ASSERT( !m_sCurrentGame.Get().empty() );
 
 	// save off old values
-	GamePrefs &gp = m_mapGameNameToGamePrefs[m_sCurrentGame];
+	GamePrefs &gp = m_mapGameNameToGamePrefs.at(m_sCurrentGame);
 	gp.m_sAnnouncer = m_sAnnouncer;
 	gp.m_sTheme = m_sTheme;
 	gp.m_sDefaultModifiers = m_sDefaultModifiers;