diff --git a/ATPDocs/deploy/capacity-planning.md b/ATPDocs/deploy/capacity-planning.md
index 8c5e9d2802..5524abc799 100644
--- a/ATPDocs/deploy/capacity-planning.md
+++ b/ATPDocs/deploy/capacity-planning.md
@@ -22,7 +22,7 @@ The sizing tool measures the capacity needed for domain controllers only. There
 
 - Download the [Defender for Identity sizing tool](<https://aka.ms/mdi/sizingtool>).
 - Review the [Defender for Identity architecture](../architecture.md) article.
-- Review the [Defender for Identity prerequisites](prerequisites-sensor-version-2.md) article.
+- Review the [Defender for Identity prerequisites](prerequisites-sensor-version-2.md) article.  The Microsoft Defender for Identity Sizing Tool currently only applies to the sensor version 2.x.
 
 To ensure accurate results, only run the sizing tool *before* you've installed any Defender for Identity sensors in your environment.