diff --git a/CHANGES.rst b/CHANGES.rst
index 26e63dc4d..85516d368 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -10,6 +10,7 @@ Unreleased
 
 Fixed
 ~~~~~
+- Updating a field with a nullable data relation fails when value is null (`#1159`_)
 - ``cerberus.schema.SchemaError`` when ``VALIDATE_FILTERS = True``. (`#1154`_)
 - Serializers fails when array of types is in schema. (`#1112`_)
 - Replace the broken ``make audit`` shortcut with ``make check``, add the
@@ -52,6 +53,7 @@ Docs
 .. _`#1156`: https://github.com/pyeve/eve/issues/1156
 .. _`#1157`: https://github.com/pyeve/eve/issues/1157
 .. _`#1158`: https://github.com/pyeve/eve/issues/1158
+.. _`#1159`: https://github.com/pyeve/eve/issues/1159
 
 Version 0.8
 -----------
diff --git a/eve/io/mongo/validation.py b/eve/io/mongo/validation.py
index 6f798b8ec..417ff4646 100644
--- a/eve/io/mongo/validation.py
+++ b/eve/io/mongo/validation.py
@@ -128,6 +128,9 @@ def _validate_data_relation(self, data_relation, field, value):
                 'embeddable': {'type': 'boolean', 'default': False},
                 'version': {'type': 'boolean', 'default': False}
              }} """
+        if not value and self.schema[field].get("nullable"):
+            return
+
         if "version" in data_relation and data_relation["version"] is True:
             value_field = data_relation["field"]
             version_field = app.config["VERSION"]
diff --git a/eve/tests/methods/post.py b/eve/tests/methods/post.py
index da14beacb..201906dd7 100644
--- a/eve/tests/methods/post.py
+++ b/eve/tests/methods/post.py
@@ -888,6 +888,31 @@ def test_post_custom_json_content_type(self):
         )
         self.assert201(status)
 
+    def test_post_updating_a_document_with_nullable_data_relation_does_not_fail(self):
+        # See #1159.
+        del (self.domain["contacts"]["schema"]["ref"]["required"])
+
+        employee = {
+            "employer": {
+                "type": "objectid",
+                "nullable": True,
+                "data_relation": {"resource": self.known_resource},
+            }
+        }
+        self.app.register_resource("employee", {"schema": employee})
+
+        data = {"employer": None}
+        r, s = self.post("employee", data=data)
+        self.assert201(s)
+
+        employee["employer"]["nullable"] = False
+        r, s = self.post("employee", data=data)
+        self.assert422(s)
+
+        del (employee["employer"]["nullable"])
+        r, s = self.post("employee", data=data)
+        self.assert422(s)
+
     def perform_post(self, data, valid_items=[0]):
         r, status = self.post(self.known_resource_url, data=data)
         self.assert201(status)