diff --git a/documentation/guides/migrating-from-v8-to-v9.md b/documentation/guides/migrating-from-v8-to-v9.md
index 981d9277da6..84fa0794e70 100644
--- a/documentation/guides/migrating-from-v8-to-v9.md
+++ b/documentation/guides/migrating-from-v8-to-v9.md
@@ -149,6 +149,13 @@ A list of functions/mixins and their value equivalents or new token values.
 | `duration(slower)`               | `--p-duration-400`      |
 | `duration(slowest)`              | `--p-duration-500`      |
 
+#### `em()`
+
+This function has been deprecated, but the definition can be copied and used locally.
+| Function | Source |
+| -------- | -------------------- |
+| `em()` | [definition](https://github.com/Shopify/polaris-react/blob/b443d114d447df15d9e72914c8ca5058439a175e/documentation/guides/legacy-polaris-v8-public-api.scss#L333) |
+
 #### `easing()`
 
 | Function                     | Replacement Value/Token                |