1 files changed, 4 insertions, 2 deletions
diff --git a/src/libutil/serialise.hh b/src/libutil/serialise.hh
index 5309828bc..6f4f4c855 100644
--- a/src/libutil/serialise.hh
+++ b/src/libutil/serialise.hh
@@ -29,7 +29,8 @@ struct NullSink : Sink
     { }
 };
 
-/* A buffered abstract sink. */
+/* A buffered abstract sink. Warning: a BufferedSink should not be
+   used from multiple threads concurrently. */
 struct BufferedSink : virtual Sink
 {
     size_t bufSize, bufPos;
@@ -72,7 +73,8 @@ struct Source
 };
 
 
-/* A buffered abstract source. */
+/* A buffered abstract source. Warning: a BufferedSource should not be
+   used from multiple threads concurrently. */
 struct BufferedSource : Source
 {
     size_t bufSize, bufPosIn, bufPosOut;