diff --git a/LOSTANDFOUND.md b/LOSTANDFOUND.md
index 84efb35315..3681e04c0b 100644
--- a/LOSTANDFOUND.md
+++ b/LOSTANDFOUND.md
@@ -100,3 +100,14 @@ Author(s):
 Reason for removal:
 - code broken and excluded from all tests for a long time
 - no maintainer available
+
+### gnrc_pktbuf_duplicate_upto() [b83430aa625a1d42f11f9badf5e5cfbb8efacd99]
+Author(s):
+- Takuo Yonezawa <yonezawa.t2@gmail.com>
+- Martine S. Lenders <m.lenders@fu-berlin.de>
+
+Reason for removal:
+- broke the abstraction of `gnrc_pktbuf`
+- its only user within the RIOT code base `gnrc_ipv6_ext` was reworked in
+  f671a87fe2c539c3aecd595ae03fa4f6f209d042 so it is not needed anymore.
+- the function was deprecated in f2760c033c5f332be076b25aa212aca4007c3d65