diff --git a/readme.md b/readme.md
index adb9910..03c8a91 100644
--- a/readme.md
+++ b/readme.md
@@ -428,6 +428,10 @@ Returns `true` if `value` is an even integer.
 
 Returns `true` if `value` is an odd integer.
 
+##### .propertyKey(value)
+
+Returns `true` if `value` can be used as an object property key (either `string`, `number` or `symbol`.)
+
 ##### .any(predicate | predicate[], ...values)
 
 Using a single `predicate` argument, returns `true` if **any** of the input `values` returns true in the `predicate`:
diff --git a/source/index.ts b/source/index.ts
index 8f0700a..82822b0 100644
--- a/source/index.ts
+++ b/source/index.ts
@@ -359,6 +359,7 @@ is.nonEmptySet = <T = unknown>(value: unknown): value is Set<T> => is.set(value)
 
 is.emptyMap = (value: unknown): value is Map<never, never> => is.map(value) && value.size === 0;
 is.nonEmptyMap = <Key = unknown, Value = unknown>(value: unknown): value is Map<Key, Value> => is.map(value) && value.size > 0;
+/** Returns `true` if `value` can be used as an object property key (either a `string`, a `number` or a `symbol`.) */
 is.propertyKey = (value: unknown): value is PropertyKey => is.any([is.string, is.number, is.symbol], value);
 
 export type Predicate = (value: unknown) => boolean;