diff --git a/graphql/execution/tests/test_execute_schema.py b/graphql/execution/tests/test_execute_schema.py
index 0c7e1033..621c4ae7 100644
--- a/graphql/execution/tests/test_execute_schema.py
+++ b/graphql/execution/tests/test_execute_schema.py
@@ -1,5 +1,7 @@
 # type: ignore
 
+from itertools import starmap, repeat
+from typing import Union
 from graphql.execution import execute
 from graphql.language.parser import parse
 from graphql.type import (
@@ -51,6 +53,7 @@ def test_executes_using_a_schema():
         {
             "id": GraphQLField(GraphQLNonNull(GraphQLString)),
             "isPublished": GraphQLField(GraphQLBoolean),
+            "topic": GraphQLField(GraphQLString),
             "author": GraphQLField(BlogAuthor),
             "title": GraphQLField(GraphQLString),
             "body": GraphQLField(GraphQLString),
@@ -58,29 +61,36 @@ def test_executes_using_a_schema():
         },
     )
 
+    def _resolve_article(obj, info, id, topic):
+        return Article(id, topic)
+
+    def _resolve_feed(*_):
+        return list(starmap(Article, zip(range(1, 10 + 1), repeat("food"))))
+
     BlogQuery = GraphQLObjectType(
         "Query",
         {
             "article": GraphQLField(
                 BlogArticle,
-                args={"id": GraphQLArgument(GraphQLID)},
-                resolver=lambda obj, info, **args: Article(args["id"]),
-            ),
-            "feed": GraphQLField(
-                GraphQLList(BlogArticle),
-                resolver=lambda *_: map(Article, range(1, 10 + 1)),
+                args={
+                    "id": GraphQLArgument(GraphQLID),
+                    "topic": GraphQLArgument(GraphQLNonNull(GraphQLString)),
+                },
+                resolver=_resolve_article,
             ),
+            "feed": GraphQLField(GraphQLList(BlogArticle), resolver=_resolve_feed),
         },
     )
 
     BlogSchema = GraphQLSchema(BlogQuery)
 
     class Article(object):
-        def __init__(self, id):
-            # type: (int) -> None
+        def __init__(self, id, topic):
+            # type: (int, Union[str, None]) -> None
             self.id = id
             self.isPublished = True
             self.author = Author()
+            self.topic = "My topic is {}".format(topic or "null")
             self.title = "My Article {}".format(id)
             self.body = "This is a post"
             self.hidden = "This data is not exposed in the schema"
@@ -97,7 +107,7 @@ def pic(self, width, height):
         @property
         def recentArticle(self):
             # type: () -> Article
-            return Article(1)
+            return Article(1, "food")
 
     class Pic(object):
         def __init__(self, uid, width, height):
@@ -112,7 +122,7 @@ def __init__(self, uid, width, height):
           id,
           title
         },
-        article(id: "1") {
+        article(id: "1", topic: null) {
           ...articleFields,
           author {
             id,
@@ -132,6 +142,7 @@ def __init__(self, uid, width, height):
       fragment articleFields on Article {
         id,
         isPublished,
+        topic,
         title,
         body,
         hidden,
@@ -159,6 +170,7 @@ def __init__(self, uid, width, height):
         "article": {
             "id": "1",
             "isPublished": True,
+            "topic": "My topic is null",
             "title": "My Article 1",
             "body": "This is a post",
             "author": {
@@ -168,6 +180,7 @@ def __init__(self, uid, width, height):
                 "recentArticle": {
                     "id": "1",
                     "isPublished": True,
+                    "topic": "My topic is food",
                     "title": "My Article 1",
                     "body": "This is a post",
                     "keywords": ["foo", "bar", "1", "true", None],
diff --git a/graphql/execution/tests/test_mutations.py b/graphql/execution/tests/test_mutations.py
index d7ec17bc..b19088ca 100644
--- a/graphql/execution/tests/test_mutations.py
+++ b/graphql/execution/tests/test_mutations.py
@@ -107,7 +107,16 @@ def assert_evaluate_mutations_serially(executor=None):
       },
       fifth: immediatelyChangeTheNumber(newNumber: 5) {
         theNumber
-      }
+      },
+      sixth: immediatelyChangeTheNumber(newNumber: null) {
+        theNumber
+      },
+      seventh: immediatelyChangeTheNumber(newNumber: 100) {
+        theNumber
+      },
+      eighth: immediatelyChangeTheNumber(newNumber: null) {
+        theNumber
+      },
     }"""
     ast = parse(doc)
     result = execute(schema, ast, Root(6), operation_name="M", executor=executor)
@@ -118,6 +127,9 @@ def assert_evaluate_mutations_serially(executor=None):
         "third": {"theNumber": 3},
         "fourth": {"theNumber": 4},
         "fifth": {"theNumber": 5},
+        "sixth": {"theNumber": None},
+        "seventh": {"theNumber": 100},
+        "eighth": {"theNumber": None},
     }
 
 
diff --git a/graphql/execution/tests/test_resolve.py b/graphql/execution/tests/test_resolve.py
index d6788f38..a9e97ea2 100644
--- a/graphql/execution/tests/test_resolve.py
+++ b/graphql/execution/tests/test_resolve.py
@@ -49,6 +49,27 @@ def _test_schema(test_field):
     )
 
 
+def test_explicit_null_is_passed_to_resolver():
+    def resolver(_, __, maybe_string):
+        return 'maybe_string is "{}"'.format(maybe_string or "null")
+
+    schema = _test_schema(
+        GraphQLField(
+            GraphQLString,
+            args=OrderedDict([("maybe_string", GraphQLArgument(GraphQLString))]),
+            resolver=resolver,
+        )
+    )
+
+    result = graphql(schema, '{ test(maybe_string: "Cool") }')
+    assert not result.errors
+    assert result.data == {"test": 'maybe_string is "Cool"'}
+
+    result = graphql(schema, "{ test(maybe_string: null) }")
+    assert not result.errors
+    assert result.data == {"test": 'maybe_string is "null"'}
+
+
 def test_default_function_accesses_properties():
     # type: () -> None
     schema = _test_schema(GraphQLField(GraphQLString))
diff --git a/graphql/execution/values.py b/graphql/execution/values.py
index def1820e..a5cd7662 100644
--- a/graphql/execution/values.py
+++ b/graphql/execution/values.py
@@ -134,15 +134,16 @@ def get_argument_values(
             continue
 
         else:
-            value = value_from_ast(arg_ast.value, arg_type, variables)  # type: ignore
-            if value is None:
+            arg_name = arg_def.out_name or name  # type: ignore
+            arg_ast_value = arg_ast.value  # type: ignore
+            value = value_from_ast(arg_ast_value, arg_type, variables)  # type: ignore
+            if value is None and not isinstance(arg_ast_value, ast.NullValue):
                 if arg_def.default_value is not Undefined:
-                    value = arg_def.default_value
-                    result[arg_def.out_name or name] = value
+                    result[arg_name] = arg_def.default_value
+                else:
+                    result[arg_name] = None
             else:
-                # We use out_name as the output name for the
-                # dict if exists
-                result[arg_def.out_name or name] = value
+                result[arg_name] = value
 
     return result