diff --git a/master_changes.md b/master_changes.md
index bab3cd1bd72..c9e218820a3 100644
--- a/master_changes.md
+++ b/master_changes.md
@@ -99,6 +99,7 @@ users)
   * Unset OPAM_SWITCH_PREFIX when using make cold [#5534 @kit-ty-kate]
   * Bump the vendored opam-0install-cudf to 0.5.0 [#6130 @kit-ty-kate]
   * Require opam-0install-cudf >= 0.5.0 [#6130 @kit-ty-kate]
+  * Bump the vendored mccs to 1.1+18 [#6170 @kit-ty-kate]
 
 ## Infrastructure
 
diff --git a/src_ext/Makefile.sources b/src_ext/Makefile.sources
index 0bd663c1324..3ed5cae4811 100644
--- a/src_ext/Makefile.sources
+++ b/src_ext/Makefile.sources
@@ -22,8 +22,8 @@ MD5_cudf = ed8fea314d0c6dc0d8811ccf860c53dd
 URL_dose3 = https://gitlab.com/irill/dose3/-/archive/7.0.0/dose3-7.0.0.tar.gz
 MD5_dose3 = bc99cbcea8fca29dca3ebbee54be45e1
 
-URL_mccs = https://github.com/ocaml-opam/ocaml-mccs/archive/refs/tags/1.1+17.tar.gz
-MD5_mccs = 844d99bc531e0713238fe4b6b8511ed1
+URL_mccs = https://github.com/ocaml-opam/ocaml-mccs/releases/download/1.1+18/mccs-1.1+18.tar.gz
+MD5_mccs = 3fd6f609a02f3357f57570750fcacde0
 
 URL_opam-0install-cudf = https://github.com/ocaml-opam/opam-0install-cudf/releases/download/v0.5.0/opam-0install-cudf-0.5.0.tar.gz
 MD5_opam-0install-cudf = 75419722aa839f518a25cae1b3c6efd4