diff --git a/moto/core/responses.py b/moto/core/responses.py
index 54b575912..b6ae0270e 100644
--- a/moto/core/responses.py
+++ b/moto/core/responses.py
@@ -333,7 +333,8 @@ class BaseResponse(_TemplateEnvironmentMixin, ActionAuthenticatorMixin):
                     self.body = k
         if hasattr(request, "files") and request.files:
             for _, value in request.files.items():
-                self.body = value.stream
+                self.body = value.stream.read()
+                value.stream.close()
             if querystring.get("key"):
                 filename = os.path.basename(request.files["file"].filename)
                 querystring["key"] = [
diff --git a/tests/test_s3/test_s3_file_handles.py b/tests/test_s3/test_s3_file_handles.py
index e5a6796ed..c1e6aacc8 100644
--- a/tests/test_s3/test_s3_file_handles.py
+++ b/tests/test_s3/test_s3_file_handles.py
@@ -5,6 +5,7 @@ from functools import wraps
 from unittest import SkipTest, TestCase
 
 import boto3
+import requests
 
 from moto import mock_aws, settings
 from moto.dynamodb.models import DynamoDBBackend
@@ -311,6 +312,16 @@ class TestS3FileHandleClosuresUsingMocks(TestCase):
                 self.s3_client.put_object(Bucket="foo", Key="bar", Body="stuff")
                 self.s3_client.put_object(Bucket="foo", Key="bar", Body="stuff2")
 
+    @verify_zero_warnings
+    def test_upload_using_form(self):
+        with mock_aws():
+            self.s3_client.create_bucket(Bucket="foo")
+            requests.post(
+                "https://foo.s3.amazonaws.com/",
+                data={"key": "test-key"},
+                files={"file": ("tmp.txt", b"test content")},
+            )
+
 
 def test_verify_key_can_be_copied_after_disposing():
     # https://github.com/getmoto/moto/issues/5588