diff --git a/src/actions/receive-profile.js b/src/actions/receive-profile.js
index e8e4018dad..fa6e7e207b 100644
--- a/src/actions/receive-profile.js
+++ b/src/actions/receive-profile.js
@@ -1048,6 +1048,8 @@ export function getProfilesFromRawUrl(
         );
     }
 
+    // Profile may be null only for the `from-addon` dataSource since we do
+    // not `await` for retrieveProfileFromAddon function.
     return {
       profile: getProfileOrNull(getState()),
       shouldSetupInitialUrlState,
diff --git a/src/components/app/UrlManager.js b/src/components/app/UrlManager.js
index 6c544b1538..96caa8a96c 100644
--- a/src/components/app/UrlManager.js
+++ b/src/components/app/UrlManager.js
@@ -102,6 +102,8 @@ class UrlManager extends React.PureComponent<Props> {
       } = await getProfilesFromRawUrl(window.location);
 
       // Manually coerce these into the proper type due to the FlowFixMe above.
+      // Profile may be null only for the `from-addon` dataSource since we do
+      // not `await` for retrieveProfileFromAddon function.
       const profile: Profile | null = results.profile;
       const shouldSetupInitialUrlState: boolean =
         results.shouldSetupInitialUrlState;