diff --git a/src/GUI/MapWidget.cxx b/src/GUI/MapWidget.cxx
index e3cc5de77..b6f344497 100644
--- a/src/GUI/MapWidget.cxx
+++ b/src/GUI/MapWidget.cxx
@@ -917,7 +917,7 @@ public:
   virtual bool pass(FGPositioned* aPos) const {
     if (_fixes && (aPos->type() == FGPositioned::FIX)) {
       // ignore fixes which end in digits - expirmental
-      if (isdigit(aPos->ident()[3]) && isdigit(aPos->ident()[4])) {
+      if (aPos->ident().length() > 4 && isdigit(aPos->ident()[3]) && isdigit(aPos->ident()[4])) {
         return false;
       }
     }