diff --git a/packages/client-core/src/cancelablePromise.ts b/packages/client-core/src/cancelablePromise.ts
index f002b69e9..cc7f31fce 100644
--- a/packages/client-core/src/cancelablePromise.ts
+++ b/packages/client-core/src/cancelablePromise.ts
@@ -80,7 +80,7 @@ export class CancelablePromise<T> implements Promise<T> {
     });
   }
 
-  get [Symbol.toStringTag]() {
+  get [Symbol.toStringTag](): string {
     return 'Cancellable Promise';
   }
 
diff --git a/packages/openapi-ts/src/templates/core/CancelablePromise.hbs b/packages/openapi-ts/src/templates/core/CancelablePromise.hbs
index 15256dde3..5c10c4ed6 100644
--- a/packages/openapi-ts/src/templates/core/CancelablePromise.hbs
+++ b/packages/openapi-ts/src/templates/core/CancelablePromise.hbs
@@ -80,7 +80,7 @@ export class CancelablePromise<T> implements Promise<T> {
 		});
 	}
 
-	get [Symbol.toStringTag]() {
+	get [Symbol.toStringTag](): string {
 		return "Cancellable Promise";
 	}
 
diff --git a/packages/openapi-ts/test/__snapshots__/test/generated/v2/core/CancelablePromise.ts.snap b/packages/openapi-ts/test/__snapshots__/test/generated/v2/core/CancelablePromise.ts.snap
index ccc082e8f..5c10c4ed6 100644
--- a/packages/openapi-ts/test/__snapshots__/test/generated/v2/core/CancelablePromise.ts.snap
+++ b/packages/openapi-ts/test/__snapshots__/test/generated/v2/core/CancelablePromise.ts.snap
@@ -80,7 +80,7 @@ export class CancelablePromise<T> implements Promise<T> {
 		});
 	}
 
-	get [Symbol.toStringTag]() {
+	get [Symbol.toStringTag](): string {
 		return "Cancellable Promise";
 	}
 
@@ -123,4 +123,4 @@ export class CancelablePromise<T> implements Promise<T> {
 	public get isCancelled(): boolean {
 		return this._isCancelled;
 	}
-}
\ No newline at end of file
+}
diff --git a/packages/openapi-ts/test/__snapshots__/test/generated/v3/core/CancelablePromise.ts.snap b/packages/openapi-ts/test/__snapshots__/test/generated/v3/core/CancelablePromise.ts.snap
index ccc082e8f..5c10c4ed6 100644
--- a/packages/openapi-ts/test/__snapshots__/test/generated/v3/core/CancelablePromise.ts.snap
+++ b/packages/openapi-ts/test/__snapshots__/test/generated/v3/core/CancelablePromise.ts.snap
@@ -80,7 +80,7 @@ export class CancelablePromise<T> implements Promise<T> {
 		});
 	}
 
-	get [Symbol.toStringTag]() {
+	get [Symbol.toStringTag](): string {
 		return "Cancellable Promise";
 	}
 
@@ -123,4 +123,4 @@ export class CancelablePromise<T> implements Promise<T> {
 	public get isCancelled(): boolean {
 		return this._isCancelled;
 	}
-}
\ No newline at end of file
+}
diff --git a/packages/openapi-ts/test/__snapshots__/test/generated/v3_axios/core/CancelablePromise.ts.snap b/packages/openapi-ts/test/__snapshots__/test/generated/v3_axios/core/CancelablePromise.ts.snap
index ccc082e8f..5c10c4ed6 100644
--- a/packages/openapi-ts/test/__snapshots__/test/generated/v3_axios/core/CancelablePromise.ts.snap
+++ b/packages/openapi-ts/test/__snapshots__/test/generated/v3_axios/core/CancelablePromise.ts.snap
@@ -80,7 +80,7 @@ export class CancelablePromise<T> implements Promise<T> {
 		});
 	}
 
-	get [Symbol.toStringTag]() {
+	get [Symbol.toStringTag](): string {
 		return "Cancellable Promise";
 	}
 
@@ -123,4 +123,4 @@ export class CancelablePromise<T> implements Promise<T> {
 	public get isCancelled(): boolean {
 		return this._isCancelled;
 	}
-}
\ No newline at end of file
+}
diff --git a/packages/openapi-ts/test/__snapshots__/test/generated/v3_client/core/CancelablePromise.ts.snap b/packages/openapi-ts/test/__snapshots__/test/generated/v3_client/core/CancelablePromise.ts.snap
index ccc082e8f..5c10c4ed6 100644
--- a/packages/openapi-ts/test/__snapshots__/test/generated/v3_client/core/CancelablePromise.ts.snap
+++ b/packages/openapi-ts/test/__snapshots__/test/generated/v3_client/core/CancelablePromise.ts.snap
@@ -80,7 +80,7 @@ export class CancelablePromise<T> implements Promise<T> {
 		});
 	}
 
-	get [Symbol.toStringTag]() {
+	get [Symbol.toStringTag](): string {
 		return "Cancellable Promise";
 	}
 
@@ -123,4 +123,4 @@ export class CancelablePromise<T> implements Promise<T> {
 	public get isCancelled(): boolean {
 		return this._isCancelled;
 	}
-}
\ No newline at end of file
+}
diff --git a/packages/openapi-ts/test/__snapshots__/test/generated/v3_enums_typescript/core/CancelablePromise.ts.snap b/packages/openapi-ts/test/__snapshots__/test/generated/v3_enums_typescript/core/CancelablePromise.ts.snap
index ccc082e8f..5c10c4ed6 100644
--- a/packages/openapi-ts/test/__snapshots__/test/generated/v3_enums_typescript/core/CancelablePromise.ts.snap
+++ b/packages/openapi-ts/test/__snapshots__/test/generated/v3_enums_typescript/core/CancelablePromise.ts.snap
@@ -80,7 +80,7 @@ export class CancelablePromise<T> implements Promise<T> {
 		});
 	}
 
-	get [Symbol.toStringTag]() {
+	get [Symbol.toStringTag](): string {
 		return "Cancellable Promise";
 	}
 
@@ -123,4 +123,4 @@ export class CancelablePromise<T> implements Promise<T> {
 	public get isCancelled(): boolean {
 		return this._isCancelled;
 	}
-}
\ No newline at end of file
+}
diff --git a/packages/openapi-ts/test/__snapshots__/test/generated/v3_legacy_positional_args/core/CancelablePromise.ts.snap b/packages/openapi-ts/test/__snapshots__/test/generated/v3_legacy_positional_args/core/CancelablePromise.ts.snap
index ccc082e8f..5c10c4ed6 100644
--- a/packages/openapi-ts/test/__snapshots__/test/generated/v3_legacy_positional_args/core/CancelablePromise.ts.snap
+++ b/packages/openapi-ts/test/__snapshots__/test/generated/v3_legacy_positional_args/core/CancelablePromise.ts.snap
@@ -80,7 +80,7 @@ export class CancelablePromise<T> implements Promise<T> {
 		});
 	}
 
-	get [Symbol.toStringTag]() {
+	get [Symbol.toStringTag](): string {
 		return "Cancellable Promise";
 	}
 
@@ -123,4 +123,4 @@ export class CancelablePromise<T> implements Promise<T> {
 	public get isCancelled(): boolean {
 		return this._isCancelled;
 	}
-}
\ No newline at end of file
+}
diff --git a/packages/openapi-ts/test/__snapshots__/test/generated/v3_node/core/CancelablePromise.ts.snap b/packages/openapi-ts/test/__snapshots__/test/generated/v3_node/core/CancelablePromise.ts.snap
index ccc082e8f..5c10c4ed6 100644
--- a/packages/openapi-ts/test/__snapshots__/test/generated/v3_node/core/CancelablePromise.ts.snap
+++ b/packages/openapi-ts/test/__snapshots__/test/generated/v3_node/core/CancelablePromise.ts.snap
@@ -80,7 +80,7 @@ export class CancelablePromise<T> implements Promise<T> {
 		});
 	}
 
-	get [Symbol.toStringTag]() {
+	get [Symbol.toStringTag](): string {
 		return "Cancellable Promise";
 	}
 
@@ -123,4 +123,4 @@ export class CancelablePromise<T> implements Promise<T> {
 	public get isCancelled(): boolean {
 		return this._isCancelled;
 	}
-}
\ No newline at end of file
+}
diff --git a/packages/openapi-ts/test/__snapshots__/test/generated/v3_options/core/CancelablePromise.ts.snap b/packages/openapi-ts/test/__snapshots__/test/generated/v3_options/core/CancelablePromise.ts.snap
index ccc082e8f..5c10c4ed6 100644
--- a/packages/openapi-ts/test/__snapshots__/test/generated/v3_options/core/CancelablePromise.ts.snap
+++ b/packages/openapi-ts/test/__snapshots__/test/generated/v3_options/core/CancelablePromise.ts.snap
@@ -80,7 +80,7 @@ export class CancelablePromise<T> implements Promise<T> {
 		});
 	}
 
-	get [Symbol.toStringTag]() {
+	get [Symbol.toStringTag](): string {
 		return "Cancellable Promise";
 	}
 
@@ -123,4 +123,4 @@ export class CancelablePromise<T> implements Promise<T> {
 	public get isCancelled(): boolean {
 		return this._isCancelled;
 	}
-}
\ No newline at end of file
+}
diff --git a/packages/openapi-ts/test/__snapshots__/test/generated/v3_xhr/core/CancelablePromise.ts.snap b/packages/openapi-ts/test/__snapshots__/test/generated/v3_xhr/core/CancelablePromise.ts.snap
index ccc082e8f..5c10c4ed6 100644
--- a/packages/openapi-ts/test/__snapshots__/test/generated/v3_xhr/core/CancelablePromise.ts.snap
+++ b/packages/openapi-ts/test/__snapshots__/test/generated/v3_xhr/core/CancelablePromise.ts.snap
@@ -80,7 +80,7 @@ export class CancelablePromise<T> implements Promise<T> {
 		});
 	}
 
-	get [Symbol.toStringTag]() {
+	get [Symbol.toStringTag](): string {
 		return "Cancellable Promise";
 	}
 
@@ -123,4 +123,4 @@ export class CancelablePromise<T> implements Promise<T> {
 	public get isCancelled(): boolean {
 		return this._isCancelled;
 	}
-}
\ No newline at end of file
+}