diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index b29cd0627d05c..bb645e14fdd5d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -71,6 +71,15 @@ future versions of Clang.
 
 - ...
 
+Modified Compiler Flags
+-----------------------
+
+- Before Clang 7.0, we prepended the "#" character to the --autocomplete argument to
+enable cc1 flags. For example, when the -cc1 or -Xclang flag is in the clang invocation,
+the shell executed clang --autocomplete=#-<flag to be completed>. Clang 7.0 now
+requires the whole invocation including all flags to be passed to the --autocomplete
+like this: clang --autocomplete=-cc1,-xc++,-fsyn.
+
 New Pragmas in Clang
 -----------------------