diff --git a/ifstools/handlers/GenericFile.py b/ifstools/handlers/GenericFile.py
index e6a58ac..3901f1c 100644
--- a/ifstools/handlers/GenericFile.py
+++ b/ifstools/handlers/GenericFile.py
@@ -8,7 +8,13 @@ from .. import utils
 
 class GenericFile(Node):
     def from_xml(self, element):
-        self.start, self.size, self.time = self._split_ints(element.text)
+        info = self._split_ints(element.text)
+        # sometimes we don't get a timestamp
+        if len(info) == 2:
+            self.start, self.size = info
+            self.time = -1
+        else:
+            self.start, self.size, self.time = info
 
     def from_filesystem(self, folder):
         self.base_path = self.parent.base_path
diff --git a/ifstools/utils.py b/ifstools/utils.py
index d499846..90ce88f 100644
--- a/ifstools/utils.py
+++ b/ifstools/utils.py
@@ -21,4 +21,6 @@ def save_with_timestamp(filename, data, timestamp):
     mkdir_silent(os.path.dirname(filename))
     with open(filename, 'wb') as f:
         f.write(data)
-    os.utime(filename, (timestamp,timestamp))
+    # we store invalid timestamps as -1
+    if timestamp >= 0:
+        os.utime(filename, (timestamp,timestamp))