diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1af4996d2b..f64a2f3b54 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,10 @@ incremented for features.
 
 ## [Unreleased]
 
+### Fixes
+
+* ts: Allow nullable types for `Option<T>` mapped types ([#1428](https://github.com/project-serum/anchor/pull/1428)).
+
 ### Breaking
 
 * lang: Enforce that the payer for an init-ed account be marked `mut` ([#1271](https://github.com/project-serum/anchor/pull/1271)).
diff --git a/ts/src/program/namespace/types.ts b/ts/src/program/namespace/types.ts
index 5c80411abc..be278dfde6 100644
--- a/ts/src/program/namespace/types.ts
+++ b/ts/src/program/namespace/types.ts
@@ -107,7 +107,7 @@ export type DecodeType<T extends IdlType, Defined> = T extends keyof TypeMap
   : T extends { option: { defined: keyof Defined } }
   ? Defined[T["option"]["defined"]] | null
   : T extends { option: keyof TypeMap }
-  ? TypeMap[T["option"]]
+  ? TypeMap[T["option"]] | null
   : T extends { vec: keyof TypeMap }
   ? TypeMap[T["vec"]][]
   : T extends { array: [defined: keyof TypeMap, size: number] }