diff --git a/src/caosdb/common/models.py b/src/caosdb/common/models.py
index 39d9e38d5c9d0d943af83e075a3923de2b0d7bd7..c9461b0683f52b0d8230253f12a80f83a637535f 100644
--- a/src/caosdb/common/models.py
+++ b/src/caosdb/common/models.py
@@ -856,6 +856,8 @@ class Entity(object):
                     xml.append(v_elem)
             elif self.value == "":
                 xml.append(etree.Element("EmptyString"))
+            elif str(self.value) == "nan":
+                xml.text = "NaN"
             else:
                 xml.text = str(self.value)