diff --git a/PROCESSORS.md b/PROCESSORS.md
index 960043c..f7d6b0f 100644
--- a/PROCESSORS.md
+++ b/PROCESSORS.md
@@ -619,6 +619,24 @@ You can use `update_resource` to rename a resource like so:
   update_resource('current-name', name='new-name')
 ```
 
+#### update_schema.py
+Update schema properties for one or more resources in the package
+
+```python
+def update_schema(resources, **metadata):
+    pass
+```
+
+- `resources`
+  - A name of a resource to operate on
+  - A regular expression matching resource names
+  - A list of resource names
+  - `None` indicates operation should be done on all resources
+  - The index of the resource in the package
+- `metadata` - Any allowed schema property (according to the [spec]([https://frictionlessdata.io/specs/table-schema/#descriptor)) can be provided here.
+
+You can use `update_schema` to add a `missingValues` property, change the primary key etc.
+
 #### set_primary_key.py
 Updates the primary key for one or more resources in the package
 
diff --git a/dataflows/VERSION b/dataflows/VERSION
index ff8026f..9c3f756 100644
--- a/dataflows/VERSION
+++ b/dataflows/VERSION
@@ -1 +1 @@
-0.0.66
+0.0.67
diff --git a/dataflows/base/schema_validator.py b/dataflows/base/schema_validator.py
index 7d11c9a..7cb643f 100644
--- a/dataflows/base/schema_validator.py
+++ b/dataflows/base/schema_validator.py
@@ -52,3 +52,8 @@ def schema_validator(resource, iterator,
                 continue
 
         yield row
+
+
+schema_validator.drop = drop
+schema_validator.ignore = ignore
+schema_validator.raise_exception = raise_exception
diff --git a/dataflows/processors/__init__.py b/dataflows/processors/__init__.py
index 3e62caa..3008426 100644
--- a/dataflows/processors/__init__.py
+++ b/dataflows/processors/__init__.py
@@ -22,3 +22,4 @@
 from .unstream import unstream
 from .update_package import update_package, add_metadata
 from .update_resource import update_resource
+from .update_schema import update_schema
diff --git a/dataflows/processors/update_schema.py b/dataflows/processors/update_schema.py
new file mode 100644
index 0000000..234aec6
--- /dev/null
+++ b/dataflows/processors/update_schema.py
@@ -0,0 +1,21 @@
+from dataflows import PackageWrapper
+from dataflows.helpers.resource_matcher import ResourceMatcher
+
+
+def update_schema(resources, **props):
+
+    def func(package: PackageWrapper):
+        matcher = ResourceMatcher(resources, package.pkg)
+        for resource in package.pkg.descriptor['resources']:
+            if matcher.match(resource['name']):
+                resource.setdefault('schema', {}).update(props)
+        yield package.pkg
+
+        res_iter = iter(package)
+        for r in res_iter:
+            if matcher.match(r.res.name):
+                yield r.it
+            else:
+                yield r
+
+    return func
diff --git a/tests/test_lib.py b/tests/test_lib.py
index d169736..22e51c4 100644
--- a/tests/test_lib.py
+++ b/tests/test_lib.py
@@ -763,6 +763,22 @@ def test_update_resource():
     assert dp.descriptor['resources'][4]['source'] == 'thewild'
 
 
+def test_update_schema():
+    from dataflows import Flow, printer, update_schema, validate
+
+    f = Flow(
+        [['a', '-'], ['a', 0]],
+        update_schema(-1, missingValues=['-']),
+        validate(),
+        printer()
+    )
+    results, dp, stats = f.results()
+    print(dp.descriptor)
+    assert results[0] == [
+        dict(col0='a', col1=None),
+        dict(col0='a', col1=0),
+    ]
+
 def test_set_type_resources():
     from dataflows import Flow, set_type, validate