diff --git a/src/gui/gui.cpp b/src/gui/gui.cpp
index f90102f11..ce4fde46b 100644
--- a/src/gui/gui.cpp
+++ b/src/gui/gui.cpp
@@ -4960,6 +4960,9 @@ bool FurnaceGUI::loop() {
               checkExtension(".dmf");
             }
           }
+          if (curFileDialog==GUI_FILE_SAVE_DMF_LEGACY) {
+            checkExtension(".dmf");
+          }
           if (curFileDialog==GUI_FILE_SAMPLE_SAVE ||
               curFileDialog==GUI_FILE_EXPORT_AUDIO_ONE ||
               curFileDialog==GUI_FILE_EXPORT_AUDIO_PER_SYS ||