diff --git a/roomserver/roomserver.go b/roomserver/roomserver.go
index 4685f474f..65523e3c2 100644
--- a/roomserver/roomserver.go
+++ b/roomserver/roomserver.go
@@ -28,6 +28,9 @@ import (
 )
 
 // NewInternalAPI returns a concrete implementation of the internal API.
+//
+// Many of the methods provided by this API depend on access to a federation API, and so
+// you may wish to call `SetFederationAPI` on the returned struct to avoid nil-dereference errors.
 func NewInternalAPI(
 	processContext *process.ProcessContext,
 	cfg *config.Dendrite,
diff --git a/userapi/userapi.go b/userapi/userapi.go
index 6dcbc121f..c47c6f001 100644
--- a/userapi/userapi.go
+++ b/userapi/userapi.go
@@ -36,6 +36,9 @@ import (
 
 // NewInternalAPI returns a concrete implementation of the internal API. Callers
 // can call functions directly on the returned API or via an HTTP interface using AddInternalRoutes.
+//
+// Creating a new instance of the user API requires a roomserver API with a federation API set
+// using its `SetFederationAPI` method, other you may get nil-dereference errors.
 func NewInternalAPI(
 	processContext *process.ProcessContext,
 	dendriteCfg *config.Dendrite,