diff --git a/moto/kms/utils.py b/moto/kms/utils.py
index 4e7527611..0d63d052c 100644
--- a/moto/kms/utils.py
+++ b/moto/kms/utils.py
@@ -379,6 +379,10 @@ def encrypt(
         raise ValidationException(
             "1 validation error detected: Value at 'plaintext' failed to satisfy constraint: Member must have length greater than or equal to 1"
         )
+    if len(plaintext) > 4096:
+        raise ValidationException(
+            "1 validation error detected: Value at 'plaintext' failed to satisfy constraint: Member must have length less than or equal to 4096"
+        )
 
     iv = os.urandom(IV_LEN)
     aad = _serialize_encryption_context(encryption_context=encryption_context)
diff --git a/tests/test_kms/__init__.py b/tests/test_kms/__init__.py
index 08a1c1568..b52dd9f4e 100644
--- a/tests/test_kms/__init__.py
+++ b/tests/test_kms/__init__.py
@@ -1 +1,28 @@
-# This file is intentionally left blank.
+import os
+from functools import wraps
+
+from moto import mock_kms
+
+
+def kms_aws_verified(func):
+    """
+    Function that is verified to work against AWS.
+    Can be run against AWS at any time by setting:
+      MOTO_TEST_ALLOW_AWS_REQUEST=true
+
+    If this environment variable is not set, the function runs in a `mock_kms` context.
+    """
+
+    @wraps(func)
+    def pagination_wrapper():
+        allow_aws_request = (
+            os.environ.get("MOTO_TEST_ALLOW_AWS_REQUEST", "false").lower() == "true"
+        )
+
+        if allow_aws_request:
+            return func()
+        else:
+            with mock_kms():
+                return func()
+
+    return pagination_wrapper
diff --git a/tests/test_kms/test_kms_encrypt.py b/tests/test_kms/test_kms_encrypt.py
index 4454330f4..1ad83cffd 100644
--- a/tests/test_kms/test_kms_encrypt.py
+++ b/tests/test_kms/test_kms_encrypt.py
@@ -6,13 +6,15 @@ from botocore.exceptions import ClientError
 
 from moto import mock_kms
 
+from . import kms_aws_verified
 from .test_kms_boto3 import PLAINTEXT_VECTORS, _get_encoded_value
 
 
-@mock_kms
-def test_create_key_with_empty_content():
+@pytest.mark.aws_verified
+@kms_aws_verified
+def test_encrypt_key_with_empty_content():
     client_kms = boto3.client("kms", region_name="ap-northeast-1")
-    metadata = client_kms.create_key(Policy="my policy")["KeyMetadata"]
+    metadata = client_kms.create_key()["KeyMetadata"]
     with pytest.raises(ClientError) as exc:
         client_kms.encrypt(KeyId=metadata["KeyId"], Plaintext="")
     err = exc.value.response["Error"]
@@ -21,6 +23,23 @@ def test_create_key_with_empty_content():
         err["Message"]
         == "1 validation error detected: Value at 'plaintext' failed to satisfy constraint: Member must have length greater than or equal to 1"
     )
+    client_kms.schedule_key_deletion(KeyId=metadata["KeyId"], PendingWindowInDays=7)
+
+
+@pytest.mark.aws_verified
+@kms_aws_verified
+def test_encrypt_key_with_large_content():
+    client_kms = boto3.client("kms", region_name="ap-northeast-1")
+    metadata = client_kms.create_key()["KeyMetadata"]
+    with pytest.raises(ClientError) as exc:
+        client_kms.encrypt(KeyId=metadata["KeyId"], Plaintext=b"x" * 4097)
+    err = exc.value.response["Error"]
+    assert err["Code"] == "ValidationException"
+    assert (
+        err["Message"]
+        == "1 validation error detected: Value at 'plaintext' failed to satisfy constraint: Member must have length less than or equal to 4096"
+    )
+    client_kms.schedule_key_deletion(KeyId=metadata["KeyId"], PendingWindowInDays=7)
 
 
 @pytest.mark.parametrize("plaintext", PLAINTEXT_VECTORS)