diff --git a/code/ryzom/tools/leveldesign/world_editor/world_editor/main_frm.cpp b/code/ryzom/tools/leveldesign/world_editor/world_editor/main_frm.cpp
index cca787ba8..419558c87 100644
--- a/code/ryzom/tools/leveldesign/world_editor/world_editor/main_frm.cpp
+++ b/code/ryzom/tools/leveldesign/world_editor/world_editor/main_frm.cpp
@@ -468,12 +468,19 @@ void CMainFrame::onLogicChanged(const std::vector<NLLIGO::CPrimRegion*> &regions
 
 bool CMainFrame::yesNoMessage (const char *format, ... )
 {
-	// Make a buffer string
-	va_list args;
-	va_start( args, format );
 	char buffer[1024];
-	sint ret = vsnprintf( buffer, 1024, format, args );
-	va_end( args );
+
+	if (format)
+	{
+		va_list args;
+		va_start( args, format );
+		sint ret = vsnprintf( buffer, 1024, format, args );
+		va_end( args );
+	}
+	else
+	{
+		strcpy(buffer, "Unknown error");
+	}
 
 	return theApp.yesNoMessage (buffer);
 }
@@ -482,12 +489,19 @@ bool CMainFrame::yesNoMessage (const char *format, ... )
 
 void CMainFrame::errorMessage (const char *format, ... )
 {
-	// Make a buffer string
-	va_list args;
-	va_start( args, format );
 	char buffer[1024];
-	sint ret = vsnprintf( buffer, 1024, format, args );
-	va_end( args );
+
+	if (format)
+	{
+		va_list args;
+		va_start( args, format );
+		sint ret = vsnprintf( buffer, 1024, format, args );
+		va_end( args );
+	}
+	else
+	{
+		strcpy(buffer, "Unknown error");
+	}
 
 	theApp.errorMessage (buffer);
 }
@@ -496,12 +510,19 @@ void CMainFrame::errorMessage (const char *format, ... )
 
 void CMainFrame::infoMessage (const char *format, ... )
 {
-	// Make a buffer string
-	va_list args;
-	va_start( args, format );
 	char buffer[1024];
-	sint ret = vsnprintf( buffer, 1024, format, args );
-	va_end( args );
+
+	if (format)
+	{
+		va_list args;
+		va_start( args, format );
+		sint ret = vsnprintf( buffer, 1024, format, args );
+		va_end( args );
+	}
+	else
+	{
+		strcpy(buffer, "Unknown error");
+	}
 
 	theApp.infoMessage (buffer);
 }
diff --git a/code/ryzom/tools/leveldesign/world_editor/world_editor/world_editor.cpp b/code/ryzom/tools/leveldesign/world_editor/world_editor/world_editor.cpp
index 3dfee3eed..b2fcee810 100644
--- a/code/ryzom/tools/leveldesign/world_editor/world_editor/world_editor.cpp
+++ b/code/ryzom/tools/leveldesign/world_editor/world_editor/world_editor.cpp
@@ -430,47 +430,76 @@ void CWorldEditorApp::OnAppAbout()
 
 bool CWorldEditorApp::yesNoMessage (const char *format, ... )
 {
-	// Make a buffer string
-	va_list args;
-	va_start( args, format );
 	char buffer[1024];
-	sint ret = vsnprintf( buffer, 1024, format, args );
-	va_end( args );
+
+	if (format)
+	{
+		va_list args;
+		va_start( args, format );
+		sint ret = vsnprintf( buffer, 1024, format, args );
+		va_end( args );
+	}
+	else
+	{
+		strcpy(buffer, "Unknown error");
+	}
 
 	return MessageBox (m_pMainWnd?m_pMainWnd->m_hWnd:NULL, buffer, "NeL World Editor", MB_YESNO|MB_ICONQUESTION) == IDYES;
 }
 
 void CWorldEditorApp::errorMessage (const char *format, ... )
 {
-	// Make a buffer string
-	va_list args;
-	va_start( args, format );
 	char buffer[1024];
-	sint ret = vsnprintf( buffer, 1024, format, args );
-	va_end( args );
+
+	if (format)
+	{
+		va_list args;
+		va_start( args, format );
+		sint ret = vsnprintf( buffer, 1024, format, args );
+		va_end( args );
+	}
+	else
+	{
+		strcpy(buffer, "Unknown error");
+	}
 
 	MessageBox (m_pMainWnd?m_pMainWnd->m_hWnd:NULL, buffer, "NeL World Editor", MB_OK|MB_ICONEXCLAMATION);
 }
 
 void CWorldEditorApp::infoMessage (const char *format, ... )
 {
-	// Make a buffer string
-	va_list args;
-	va_start( args, format );
 	char buffer[1024];
-	sint ret = vsnprintf( buffer, 1024, format, args );
-	va_end( args );
+
+	if (format)
+	{
+		va_list args;
+		va_start( args, format );
+		sint ret = vsnprintf( buffer, 1024, format, args );
+		va_end( args );
+	}
+	else
+	{
+		strcpy(buffer, "Unknown error");
+	}
 
 	MessageBox (m_pMainWnd?m_pMainWnd->m_hWnd:NULL, buffer, "NeL World Editor", MB_OK|MB_ICONINFORMATION);
 }
 
 void CWorldEditorApp::syntaxError (const char *filename, xmlNodePtr xmlNode, const char *format, ...)
 {
-	va_list args;
-	va_start( args, format );
 	char buffer[1024];
-	sint ret = vsnprintf( buffer, 1024, format, args );
-	va_end( args );
+
+	if (format)
+	{
+		va_list args;
+		va_start( args, format );
+		sint ret = vsnprintf( buffer, 1024, format, args );
+		va_end( args );
+	}
+	else
+	{
+		strcpy(buffer, "Unknown error");
+	}
 
 	errorMessage ("(%s), node (%s), line (%d) :\n%s", filename, xmlNode->name, (int)xmlNode->content, buffer);
 }
@@ -784,12 +813,19 @@ CNoInteraction::~CNoInteraction ()
 
 void CMyLigoConfig::errorMessage (const char *format, ... )
 {
-	// Make a buffer string
-	va_list args;
-	va_start( args, format );
 	char buffer[1024];
-	sint ret = vsnprintf( buffer, 1024, format, args );
-	va_end( args );
+
+	if (format)
+	{
+		va_list args;
+		va_start( args, format );
+		sint ret = vsnprintf( buffer, 1024, format, args );
+		va_end( args );
+	}
+	else
+	{
+		strcpy(buffer, "Unknown error");
+	}
 
 	theApp.errorMessage (buffer);
 }
diff --git a/code/ryzom/tools/leveldesign/world_editor/world_editor_shard_monitor_plugin/plugin.cpp b/code/ryzom/tools/leveldesign/world_editor/world_editor_shard_monitor_plugin/plugin.cpp
index ba0fcfb6a..c55a6f178 100644
--- a/code/ryzom/tools/leveldesign/world_editor/world_editor_shard_monitor_plugin/plugin.cpp
+++ b/code/ryzom/tools/leveldesign/world_editor/world_editor_shard_monitor_plugin/plugin.cpp
@@ -1093,11 +1093,19 @@ void CPlugin::postRender(CDisplay &display)
 
 bool CPlugin::yesNoMessage (const char *format, ... )
 {
-	va_list args;
-	va_start( args, format );
 	char buffer[1024];
-	sint ret = vsnprintf( buffer, 1024, format, args );
-	va_end( args );
+
+	if (format)
+	{
+		va_list args;
+		va_start( args, format );
+		sint ret = vsnprintf( buffer, 1024, format, args );
+		va_end( args );
+	}
+	else
+	{
+		strcpy(buffer, "Unknown error");
+	}
 
 	return _PluginAccess->yesNoMessage ("Plugin AI : %s", buffer);
 }
@@ -1106,11 +1114,19 @@ bool CPlugin::yesNoMessage (const char *format, ... )
 
 void CPlugin::errorMessage (const char *format, ... )
 {
-	va_list args;
-	va_start( args, format );
 	char buffer[1024];
-	sint ret = vsnprintf( buffer, 1024, format, args );
-	va_end( args );
+
+	if (format)
+	{
+		va_list args;
+		va_start( args, format );
+		sint ret = vsnprintf( buffer, 1024, format, args );
+		va_end( args );
+	}
+	else
+	{
+		strcpy(buffer, "Unknown error");
+	}
 
 	_PluginAccess->errorMessage ("Plugin AI : %s", buffer);
 }
@@ -1119,11 +1135,19 @@ void CPlugin::errorMessage (const char *format, ... )
 
 void CPlugin::infoMessage (const char *format, ... )
 {
-	va_list args;
-	va_start( args, format );
 	char buffer[1024];
-	sint ret = vsnprintf( buffer, 1024, format, args );
-	va_end( args );
+
+	if (format)
+	{
+		va_list args;
+		va_start( args, format );
+		sint ret = vsnprintf( buffer, 1024, format, args );
+		va_end( args );
+	}
+	else
+	{
+		strcpy(buffer, "Unknown error");
+	}
 
 	_PluginAccess->infoMessage ("Plugin AI : %s", buffer);
 }