diff --git a/render_kdenlive.py b/render_kdenlive.py
index 92a5f15..82948f5 100644
--- a/render_kdenlive.py
+++ b/render_kdenlive.py
@@ -13,10 +13,15 @@ def get_propery(element, name):
 
 
 def melt_xml(file):
-    if file in _CACHE:
-        out = _CACHE[file]
-    else:
-        out = _CACHE[file] = subprocess.check_output(['melt', file, '-consumer', 'xml']).decode()
+    out = None
+    real_path = os.path.realpath(path)
+    if file in _CACHE and isinstance(_CACHE[file], list)
+        ts, out = _CACHE[file]
+        if os.stat(real_path).st_mtime != ts:
+            out = None
+    if not out:
+        out = subprocess.check_output(['melt', file, '-consumer', 'xml']).decode()
+        _CACHE[file] = [os.stat(real_path).st_mtime, out]
     return out