diff --git a/moto/ec2/exceptions.py b/moto/ec2/exceptions.py
index e7328ff1d..677d2f939 100644
--- a/moto/ec2/exceptions.py
+++ b/moto/ec2/exceptions.py
@@ -481,6 +481,14 @@ class CidrLimitExceeded(EC2ClientError):
         )
 
 
+class UnsupportedTenancy(EC2ClientError):
+    def __init__(self, tenancy):
+        super(UnsupportedTenancy, self).__init__(
+            "UnsupportedTenancy",
+            "The tenancy value {0} is not supported.".format(tenancy),
+        )
+
+
 class OperationNotPermitted(EC2ClientError):
     def __init__(self, association_id):
         super(OperationNotPermitted, self).__init__(
diff --git a/moto/ec2/models.py b/moto/ec2/models.py
index 72232b9eb..88be042d9 100644
--- a/moto/ec2/models.py
+++ b/moto/ec2/models.py
@@ -38,6 +38,7 @@ from os import listdir
 
 from .exceptions import (
     CidrLimitExceeded,
+    UnsupportedTenancy,
     DependencyViolationError,
     EC2ClientError,
     FilterNotImplementedError,
@@ -2941,6 +2942,10 @@ class VPC(TaggedEC2Resource, CloudFormationModel):
                 amazon_provided_ipv6_cidr_block=amazon_provided_ipv6_cidr_block,
             )
 
+    @property
+    def owner_id(self):
+        return ACCOUNT_ID
+
     @staticmethod
     def cloudformation_name_type():
         return None
@@ -3011,11 +3016,25 @@ class VPC(TaggedEC2Resource, CloudFormationModel):
         else:
             return super(VPC, self).get_filter_value(filter_name, "DescribeVpcs")
 
+    def modify_vpc_tenancy(self, tenancy):
+        if tenancy != "default":
+            raise UnsupportedTenancy(tenancy)
+        self.instance_tenancy = tenancy
+        return True
+
     def associate_vpc_cidr_block(
         self, cidr_block, amazon_provided_ipv6_cidr_block=False
     ):
         max_associations = 5 if not amazon_provided_ipv6_cidr_block else 1
 
+        for cidr in self.cidr_block_association_set.copy():
+            if (
+                self.cidr_block_association_set.get(cidr)
+                .get("cidr_block_state")
+                .get("state")
+                == "disassociated"
+            ):
+                self.cidr_block_association_set.pop(cidr)
         if (
             len(self.get_cidr_block_association_set(amazon_provided_ipv6_cidr_block))
             >= max_associations
@@ -3199,6 +3218,10 @@ class VPCBackend(object):
         else:
             raise InvalidParameterValueError(attr_name)
 
+    def modify_vpc_tenancy(self, vpc_id, tenancy):
+        vpc = self.get_vpc(vpc_id)
+        return vpc.modify_vpc_tenancy(tenancy)
+
     def enable_vpc_classic_link(self, vpc_id):
         vpc = self.get_vpc(vpc_id)
         return vpc.enable_vpc_classic_link()
diff --git a/moto/ec2/responses/vpcs.py b/moto/ec2/responses/vpcs.py
index cc553fd3b..06ebce63f 100644
--- a/moto/ec2/responses/vpcs.py
+++ b/moto/ec2/responses/vpcs.py
@@ -51,6 +51,13 @@ class VPCs(BaseResponse):
         template = self.response_template(DESCRIBE_VPCS_RESPONSE)
         return template.render(vpcs=vpcs, doc_date=doc_date)
 
+    def modify_vpc_tenancy(self):
+        vpc_id = self._get_param("VpcId")
+        tenancy = self._get_param("InstanceTenancy")
+        value = self.ec2_backend.modify_vpc_tenancy(vpc_id, tenancy)
+        template = self.response_template(MODIFY_VPC_TENANCY_RESPONSE)
+        return template.render(value=value)
+
     def describe_vpc_attribute(self):
         vpc_id = self._get_param("VpcId")
         attribute = self._get_param("Attribute")
@@ -245,6 +252,7 @@ CREATE_VPC_RESPONSE = """
         {% endif %}
       <dhcpOptionsId>{% if vpc.dhcp_options %}{{ vpc.dhcp_options.id }}{% else %}dopt-1a2b3c4d2{% endif %}</dhcpOptionsId>
       <instanceTenancy>{{ vpc.instance_tenancy }}</instanceTenancy>
+      <ownerId> {{ vpc.owner_id }}</ownerId>
       <tagSet>
         {% for tag in vpc.get_tags() %}
           <item>
@@ -344,6 +352,7 @@ DESCRIBE_VPCS_RESPONSE = """
         <dhcpOptionsId>{% if vpc.dhcp_options %}{{ vpc.dhcp_options.id }}{% else %}dopt-7a8b9c2d{% endif %}</dhcpOptionsId>
         <instanceTenancy>{{ vpc.instance_tenancy }}</instanceTenancy>
         <isDefault>{{ vpc.is_default }}</isDefault>
+        <ownerId> {{ vpc.owner_id }}</ownerId>
         <tagSet>
           {% for tag in vpc.get_tags() %}
             <item>
@@ -366,6 +375,13 @@ DELETE_VPC_RESPONSE = """
 </DeleteVpcResponse>
 """
 
+MODIFY_VPC_TENANCY_RESPONSE = """
+<ModifyVpcTenancyResponse xmlns="http://ec2.amazonaws.com/doc/2016-11-15/">
+   <requestId>7a62c49f-347e-4fc4-9331-6e8eEXAMPLE</requestId>
+   <return>true</return>
+</ModifyVpcTenancyResponse>
+"""
+
 DESCRIBE_VPC_ATTRIBUTE_RESPONSE = """
 <DescribeVpcAttributeResponse xmlns="http://ec2.amazonaws.com/doc/2016-11-15/">
   <requestId>7a62c49f-347e-4fc4-9331-6e8eEXAMPLE</requestId>
diff --git a/tests/terraform-tests.success.txt b/tests/terraform-tests.success.txt
index 2b1fad552..f32629ca2 100644
--- a/tests/terraform-tests.success.txt
+++ b/tests/terraform-tests.success.txt
@@ -61,3 +61,4 @@ TestAccAWSSsmParameterDataSource
 TestAccAWSUserGroupMembership
 TestAccAWSUserPolicyAttachment
 TestAccAWSUserSSHKey
+TestAccAWSVpc_
\ No newline at end of file