diff --git a/doc/releases/1.4.0pre1.txt b/doc/releases/1.4.0pre1.txt
index 779873f415..525ecc8f92 100644
--- a/doc/releases/1.4.0pre1.txt
+++ b/doc/releases/1.4.0pre1.txt
@@ -43,6 +43,9 @@ backwards-incompatible user-facing changes
     You can convert your existing decisions using
     ``tools/upgrade/1.4/migrate_decisions.py``.
 
+* The Probe plugin no longer strips probe output. You may need to adjust
+  your probe output if you want trailing whitespace to be removed.
+
 
 deprecated features (will be removed in a future release, likely 1.5)
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