diff --git a/panda/src/express/multifile.cxx b/panda/src/express/multifile.cxx
index e898f8f7ab..fe74484007 100644
--- a/panda/src/express/multifile.cxx
+++ b/panda/src/express/multifile.cxx
@@ -695,7 +695,7 @@ extract_subfile_to(int index, ostream &out) {
 istream &Multifile::
 open_read_subfile(int index) {
 #ifndef NDEBUG
-  ifstream empty_stream;
+  static ifstream empty_stream;
   nassertr(_open_subfile == (Subfile *)NULL, empty_stream);
   nassertr(is_read_valid(), empty_stream);
   nassertr(index >= 0 && index < (int)_subfiles.size(), empty_stream);