diff --git a/docs/ExpectAPI.md b/docs/ExpectAPI.md
index a0ac61bef2a6..b0f297bc0c51 100644
--- a/docs/ExpectAPI.md
+++ b/docs/ExpectAPI.md
@@ -1125,6 +1125,7 @@ Use `.toStrictEqual` to test that objects have the same types as well as structu
 Differences from `.toEqual`:
 
 - Keys with `undefined` properties are checked. e.g. `{a: undefined, b: 2}` does not match `{b: 2}` when using `.toStrictEqual`.
+- Array sparseness is checked. e.g. `[, 1]` does not match `[undefined, 1]` when using `.toStrictEqual`.
 - Object types are checked to be equal. e.g. A class instance with fields `a` and `b` will not equal a literal object with fields `a` and `b`.
 
 ```js