diff --git a/packages/@aws-cdk/aws-sam/test/api.test.ts b/packages/@aws-cdk/aws-sam/test/api.test.ts
new file mode 100644
index 0000000000000..bed8a90ae4e57
--- /dev/null
+++ b/packages/@aws-cdk/aws-sam/test/api.test.ts
@@ -0,0 +1,44 @@
+import '@aws-cdk/assert-internal/jest';
+import * as cdk from '@aws-cdk/core';
+import * as sam from '../lib';
+
+describe('AWS::Serverless::Api', () => {
+  let stack: cdk.Stack;
+  beforeEach(() => {
+    stack = new cdk.Stack();
+  });
+
+  test('can be created by passing a complex type to EndpointConfiguration', () => {
+    new sam.CfnApi(stack, 'Api', {
+      stageName: 'prod',
+      definitionBody: {
+        body: 'definitionBody',
+      },
+      endpointConfiguration: {
+        type: 'GLOBAL',
+      },
+    });
+
+    expect(stack).toHaveResourceLike('AWS::Serverless::Api', {
+      StageName: 'prod',
+      EndpointConfiguration: {
+        Type: 'GLOBAL',
+      },
+    });
+  });
+
+  test('can be created by passing a string to EndpointConfiguration', () => {
+    new sam.CfnApi(stack, 'Api', {
+      stageName: 'prod',
+      definitionBody: {
+        body: 'definitionBody',
+      },
+      endpointConfiguration: 'GLOBAL',
+    });
+
+    expect(stack).toHaveResourceLike('AWS::Serverless::Api', {
+      StageName: 'prod',
+      EndpointConfiguration: 'GLOBAL',
+    });
+  });
+});
diff --git a/packages/@aws-cdk/cfnspec/spec-source/901_SAM_Api_EndpointConfiguration_patch.json b/packages/@aws-cdk/cfnspec/spec-source/901_SAM_Api_EndpointConfiguration_patch.json
new file mode 100644
index 0000000000000..906dbbb88466c
--- /dev/null
+++ b/packages/@aws-cdk/cfnspec/spec-source/901_SAM_Api_EndpointConfiguration_patch.json
@@ -0,0 +1,29 @@
+{
+  "ResourceTypes": {
+    "AWS::Serverless::Api": {
+      "Properties": {
+        "EndpointConfiguration": {
+          "patch": {
+            "description": "Make the EndpointConfiguration property of AWS::Serverless::Api have a union type",
+            "operations": [
+              {
+                "op": "add",
+                "path": "/PrimitiveTypes",
+                "value": ["String"]
+              },
+              {
+                "op": "add",
+                "path": "/Types",
+                "value": ["EndpointConfiguration"]
+              },
+              {
+                "op": "remove",
+                "path": "/Type"
+              }
+            ]
+          }
+        }
+      }
+    }
+  }
+}
diff --git a/packages/@aws-cdk/cloudformation-include/test/serverless-transform.test.ts b/packages/@aws-cdk/cloudformation-include/test/serverless-transform.test.ts
index 853869ec1dd24..ce0d044bb4ed3 100644
--- a/packages/@aws-cdk/cloudformation-include/test/serverless-transform.test.ts
+++ b/packages/@aws-cdk/cloudformation-include/test/serverless-transform.test.ts
@@ -54,6 +54,30 @@ describe('CDK Include for templates with SAM transform', () => {
       loadTestFileToJsObject('only-sam-function-policies-array-ddb-crud-if.yaml'),
     );
   });
+
+  test('can ingest a template with a a union-type property provided as an object, and output it unchanged', () => {
+    includeTestTemplate(stack, 'api-endpoint-config-object.yaml');
+
+    expect(stack).toMatchTemplate(
+      loadTestFileToJsObject('api-endpoint-config-object.yaml'),
+    );
+  });
+
+  test('can ingest a template with a a union-type property provided as a string, and output it unchanged', () => {
+    includeTestTemplate(stack, 'api-endpoint-config-string.yaml');
+
+    expect(stack).toMatchTemplate(
+      loadTestFileToJsObject('api-endpoint-config-string.yaml'),
+    );
+  });
+
+  test('can ingest a template with a a union-type property provided as an empty string, and output it unchanged', () => {
+    includeTestTemplate(stack, 'api-endpoint-config-string-empty.yaml');
+
+    expect(stack).toMatchTemplate(
+      loadTestFileToJsObject('api-endpoint-config-string-empty.yaml'),
+    );
+  });
 });
 
 function includeTestTemplate(scope: constructs.Construct, testTemplate: string): inc.CfnInclude {
diff --git a/packages/@aws-cdk/cloudformation-include/test/test-templates/sam/api-endpoint-config-object.yaml b/packages/@aws-cdk/cloudformation-include/test/test-templates/sam/api-endpoint-config-object.yaml
new file mode 100644
index 0000000000000..77be57c23823c
--- /dev/null
+++ b/packages/@aws-cdk/cloudformation-include/test/test-templates/sam/api-endpoint-config-object.yaml
@@ -0,0 +1,11 @@
+AWSTemplateFormatVersion: '2010-09-09'
+Transform: AWS::Serverless-2016-10-31
+Resources:
+  Api:
+    Type: AWS::Serverless::Api
+    Properties:
+      StageName: prod
+      DefinitionBody:
+        Body: DefinitionBody
+      EndpointConfiguration:
+        Type: GLOBAL
diff --git a/packages/@aws-cdk/cloudformation-include/test/test-templates/sam/api-endpoint-config-string-empty.yaml b/packages/@aws-cdk/cloudformation-include/test/test-templates/sam/api-endpoint-config-string-empty.yaml
new file mode 100644
index 0000000000000..1898e5105a864
--- /dev/null
+++ b/packages/@aws-cdk/cloudformation-include/test/test-templates/sam/api-endpoint-config-string-empty.yaml
@@ -0,0 +1,10 @@
+AWSTemplateFormatVersion: '2010-09-09'
+Transform: AWS::Serverless-2016-10-31
+Resources:
+  Api:
+    Type: AWS::Serverless::Api
+    Properties:
+      StageName: prod
+      DefinitionBody:
+        Body: DefinitionBody
+      EndpointConfiguration: '' # empty string
diff --git a/packages/@aws-cdk/cloudformation-include/test/test-templates/sam/api-endpoint-config-string.yaml b/packages/@aws-cdk/cloudformation-include/test/test-templates/sam/api-endpoint-config-string.yaml
new file mode 100644
index 0000000000000..a12949dabd226
--- /dev/null
+++ b/packages/@aws-cdk/cloudformation-include/test/test-templates/sam/api-endpoint-config-string.yaml
@@ -0,0 +1,10 @@
+AWSTemplateFormatVersion: '2010-09-09'
+Transform: AWS::Serverless-2016-10-31
+Resources:
+  Api:
+    Type: AWS::Serverless::Api
+    Properties:
+      StageName: prod
+      DefinitionBody:
+        Body: DefinitionBody
+      EndpointConfiguration: GLOBAL
diff --git a/tools/cfn2ts/lib/codegen.ts b/tools/cfn2ts/lib/codegen.ts
index f952bb34a832e..6a02f08b1e253 100644
--- a/tools/cfn2ts/lib/codegen.ts
+++ b/tools/cfn2ts/lib/codegen.ts
@@ -585,9 +585,17 @@ export default class CodeGenerator {
       this.code.closeBlock();
     }
 
-    this.code.line('properties = properties || {};');
-    this.code.line(`const ret = new ${CFN_PARSE}.FromCloudFormationPropertyObject<${typeName.fqn}>();`);
+    this.code.line('properties = properties == null ? {} : properties;');
+    // if the passed value is not an object, immediately return it,
+    // and let a validator report an error -
+    // otherwise, we'll just return an empty object for this case,
+    // which a validator might not catch
+    // (if the interface we're emitting this function for has no required properties, for example)
+    this.code.openBlock("if (typeof properties !== 'object')");
+    this.code.line(`return new ${CFN_PARSE}.FromCloudFormationResult(properties);`);
+    this.code.closeBlock();
 
+    this.code.line(`const ret = new ${CFN_PARSE}.FromCloudFormationPropertyObject<${typeName.fqn}>();`);
     const self = this;
     // class used for the visitor
     class FromCloudFormationFactoryVisitor implements genspec.PropertyVisitor<string> {