diff --git a/src/Cockpit/panel.cxx b/src/Cockpit/panel.cxx
index 25c2c44e4..18887b83b 100644
--- a/src/Cockpit/panel.cxx
+++ b/src/Cockpit/panel.cxx
@@ -1096,6 +1096,7 @@ const char *
 FGTextLayer::Chunk::getValue () const
 {
   if (test()) {
+    _buf[0] = '\0';
     switch (_type) {
     case TEXT:
       sprintf(_buf, _fmt.c_str(), _text.c_str());