diff --git a/packages/@aws-cdk/cdk/lib/cfn-reference.ts b/packages/@aws-cdk/cdk/lib/cfn-reference.ts
index 9d533f4778d79..24cb71b37aba9 100644
--- a/packages/@aws-cdk/cdk/lib/cfn-reference.ts
+++ b/packages/@aws-cdk/cdk/lib/cfn-reference.ts
@@ -1,6 +1,6 @@
 import { Reference } from "./reference";
 
-const CFN_REFERENCE_SYMBOL = Symbol('@aws-cdk/cdk.CfnReference');
+const CFN_REFERENCE_SYMBOL = Symbol.for('@aws-cdk/cdk.CfnReference');
 
 /**
  * A Token that represents a CloudFormation reference to another resource
@@ -112,4 +112,4 @@ export class CfnReference extends Reference {
 import { CfnOutput } from "./cfn-output";
 import { Construct, IConstruct } from "./construct";
 import { Stack } from "./stack";
-import { ResolveContext, Token } from "./token";
\ No newline at end of file
+import { ResolveContext, Token } from "./token";
diff --git a/packages/@aws-cdk/cdk/lib/reference.ts b/packages/@aws-cdk/cdk/lib/reference.ts
index e9a91da8c4967..791f67c7945e4 100644
--- a/packages/@aws-cdk/cdk/lib/reference.ts
+++ b/packages/@aws-cdk/cdk/lib/reference.ts
@@ -1,6 +1,6 @@
 import { Token } from "./token";
 
-const REFERENCE_SYMBOL = Symbol('@aws-cdk/cdk.Reference');
+const REFERENCE_SYMBOL = Symbol.for('@aws-cdk/cdk.Reference');
 
 /**
  * A Token that represents a reference between two constructs
@@ -24,4 +24,4 @@ export class Reference extends Token {
   }
 }
 
-import { Construct } from "./construct";
\ No newline at end of file
+import { Construct } from "./construct";
diff --git a/packages/@aws-cdk/cdk/lib/stack.ts b/packages/@aws-cdk/cdk/lib/stack.ts
index ed1023ffaee36..ed63d77e9e5d7 100644
--- a/packages/@aws-cdk/cdk/lib/stack.ts
+++ b/packages/@aws-cdk/cdk/lib/stack.ts
@@ -42,7 +42,7 @@ export interface StackProps {
   readonly autoDeploy?: boolean;
 }
 
-const STACK_SYMBOL = Symbol('@aws-cdk/cdk.CfnReference');
+const STACK_SYMBOL = Symbol.for('@aws-cdk/cdk.Stack');
 
 /**
  * A root construct which represents a single CloudFormation stack.
@@ -66,8 +66,8 @@ export class Stack extends Construct {
    *
    * We do attribute detection since we can't reliably use 'instanceof'.
    */
-  public static isStack(x: any): x is Stack {
-    return x[STACK_SYMBOL] === true;
+  public static isStack(obj: any): obj is Stack {
+    return obj[STACK_SYMBOL] === true;
   }
 
   private static readonly VALID_STACK_NAME_REGEX = /^[A-Za-z][A-Za-z0-9-]*$/;
@@ -676,4 +676,4 @@ function findResources(roots: Iterable<IConstruct>): CfnResource[] {
 interface StackDependency {
   stack: Stack;
   reason: string;
-}
\ No newline at end of file
+}