diff --git a/include/strings.cpp b/include/strings.cpp
index c0eb89dc2..ef7defc79 100755
--- a/include/strings.cpp
+++ b/include/strings.cpp
@@ -1297,12 +1297,15 @@ bool TFilename::custom_path(const char* path_list)
   if (!is_absolute_path())
   {
 	  TToken_string pl = path_list;
-	  if (pl.empty_items())
+	  if (pl.empty())
     {
-      pl = firm2dir(prefix().get_codditta());
-	    pl << SLASH << "custom";
-      pl.add(firm2dir(-1));
-	    pl << "custom";
+      if (prefix_valid())
+      {
+        pl = firm2dir(prefix().get_codditta());
+	      pl << SLASH << "custom";
+        pl.add(firm2dir(-1));
+	      pl << "custom";
+      }
       pl.add("custom");
     }
     const TString fname = name();