diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b7374e0ef775dfa9bdb8c3f434a18660b57de0e1..a064d34e2b3449f897cc923f6e4a9d294e75b89c 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -30,14 +30,14 @@ variables:
 build-coq.8.7.0:
   <<: *template
   variables:
-    OPAM_PINS: "coq version 8.7.0   coq-mathcomp-ssreflect version 1.6.2"
+    OPAM_PINS: "coq version 8.7.0   coq-mathcomp-ssreflect version 1.6.4"
   except:
   - triggers
 
 build-coq.8.6.1:
   <<: *template
   variables:
-    OPAM_PINS: "coq version 8.6.1   coq-mathcomp-ssreflect version 1.6.2"
+    OPAM_PINS: "coq version 8.6.1   coq-mathcomp-ssreflect version 1.6.4"
 #    VALIDATE: "1" # coqchk on lambdaRust is currently broken, see Coq bug #5747
   artifacts:
     paths:
@@ -49,6 +49,6 @@ build-coq.8.6.1:
 build-iris.dev:
   <<: *template
   variables:
-    OPAM_PINS: "coq version 8.7.0   coq-mathcomp-ssreflect version 1.6.2   coq-iris.dev git https://gitlab.mpi-sws.org/FP/iris-coq.git#$IRIS_REV"
+    OPAM_PINS: "coq version 8.7.0   coq-mathcomp-ssreflect version 1.6.4   coq-iris.dev git https://gitlab.mpi-sws.org/FP/iris-coq.git#$IRIS_REV"
   only:
   - triggers
diff --git a/README.md b/README.md
index b10b862dae1705ed568c0aa7be73665057247402..11e7c135983add0d1c5a4f917a4b2d1bf215ef70 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,7 @@ This is the Coq development accompanying lambda-Rust.
 This version is known to compile with:
 
  - Coq 8.6.1 / 8.7.0
- - Ssreflect 1.6.2
+ - Ssreflect 1.6.4
  - A development version of [Iris](https://gitlab.mpi-sws.org/FP/iris-coq/)
 
 The easiest way to install the correct versions of the dependencies is through