diff --git a/lldb/docs/lldb-platform-packets.txt b/lldb/docs/lldb-platform-packets.txt
index ab4887941de1..6a01a81759e6 100644
--- a/lldb/docs/lldb-platform-packets.txt
+++ b/lldb/docs/lldb-platform-packets.txt
@@ -303,7 +303,9 @@ for the lldb testsuite to be run on a remote target device/system.
 //
 //  request packet has the fields:
 //     1. ASCII hex encoded filename
-//     2. oflags to be passed to open(2), base 16
+//     2. flags passed to the open call, base 16.
+//        Note that these are not the oflags that open(2) takes, but
+//        are the constant values in enum OpenOptions from lldb's File.h
 //     3. mode bits, base 16
 //  
 //  response is F followed by the opened file descriptor in base 10.
diff --git a/lldb/include/lldb/Host/File.h b/lldb/include/lldb/Host/File.h
index 588e6ece1ad1..69ae2004e422 100644
--- a/lldb/include/lldb/Host/File.h
+++ b/lldb/include/lldb/Host/File.h
@@ -33,6 +33,8 @@ public:
   static int kInvalidDescriptor;
   static FILE *kInvalidStream;
 
+  // NB this enum is used in the lldb platform gdb-remote packet
+  // vFile:open: and existing values cannot be modified.
   enum OpenOptions {
     eOpenOptionRead = (1u << 0),  // Open file for reading
     eOpenOptionWrite = (1u << 1), // Open file for writing