diff --git a/panda/src/express/compress_string.cxx b/panda/src/express/compress_string.cxx
index 32371958e9..892457c288 100644
--- a/panda/src/express/compress_string.cxx
+++ b/panda/src/express/compress_string.cxx
@@ -83,14 +83,14 @@ compress_file(const Filename &source, const Filename &dest, int compression_leve
     // The default is binary, if not specified otherwise.
     source_filename.set_binary();
   }
-  istream *source_stream = vfs->open_read_file(source_filename, true);
+  istream *source_stream = vfs->open_read_file(source_filename, false);
   if (source_stream == NULL) {
     express_cat.info() << "Couldn't open file " << source_filename << "\n";
     return false;
   }
   
   Filename dest_filename = Filename::binary_filename(dest);
-  ostream *dest_stream = vfs->open_write_file(dest_filename, true, true);
+  ostream *dest_stream = vfs->open_write_file(dest_filename, false, true);
   if (dest_stream == NULL) {
     express_cat.info() << "Couldn't open file " << dest_filename << "\n";
     vfs->close_read_file(source_stream);
@@ -131,7 +131,7 @@ decompress_file(const Filename &source, const Filename &dest) {
     // The default is binary, if not specified otherwise.
     dest_filename.set_binary();
   }
-  ostream *dest_stream = vfs->open_write_file(dest_filename, true, true);
+  ostream *dest_stream = vfs->open_write_file(dest_filename, false, true);
   if (dest_stream == NULL) {
     express_cat.info() << "Couldn't open file " << dest_filename << "\n";
     vfs->close_read_file(source_stream);