diff --git a/Design:-subflows.md b/Design:-subflows.md
index 3dcc803..df7dc7e 100644
--- a/Design:-subflows.md
+++ b/Design:-subflows.md
@@ -2,6 +2,8 @@ A subflow is a set of connected nodes that can be easily referenced and reused w
 
 A subflow is represented as a single node in the workspace which can be opened up in a tab to see the underlying flow.
 
+Subflows cannot contain subflows.
+
 A subflow can be used in one of two modes: (this is tbd. Might just stick with singleton for v1)
 
 1. Singleton : only one copy of the flow exists.