diff --git a/dev/ci/ci-iris-lambda-rust.sh b/dev/ci/ci-iris-lambda-rust.sh
index 63743239f744..1af0f634c49c 100755
--- a/dev/ci/ci-iris-lambda-rust.sh
+++ b/dev/ci/ci-iris-lambda-rust.sh
@@ -9,27 +9,20 @@ lambdaRust_CI_DIR="${CI_BUILD_DIR}/lambdaRust"
 
 install_ssreflect
 
-# Add or update the opam repo we need for dependency resolution
-opam repo add iris-dev https://gitlab.mpi-sws.org/FP/opam-dev.git -p 0 || opam update iris-dev
-
 # Setup lambdaRust first
 git_checkout "${lambdaRust_CI_BRANCH}" "${lambdaRust_CI_GITURL}" "${lambdaRust_CI_DIR}"
 
 # Extract required version of Iris
-Iris_VERSION=$(grep -F coq-iris < "${lambdaRust_CI_DIR}/opam" | grep -E 'dev\.([0-9a-z.-]+)' -o)
-Iris_URL=$(opam show "coq-iris.$Iris_VERSION" -f upstream-url)
-read -r -a Iris_URL_PARTS <<< "$(echo "$Iris_URL" | tr '#' ' ')"
+Iris_SHA=$(grep -F coq-iris < "${lambdaRust_CI_DIR}/opam" | sed 's/.*"dev\.[0-9.-]\+\.\([0-9a-z]\+\)".*/\1/')
 
 # Setup Iris
-git_checkout "${Iris_CI_BRANCH}" "${Iris_CI_GITURL}" "${Iris_CI_DIR}" "${Iris_URL_PARTS[1]}"
+git_checkout "${Iris_CI_BRANCH}" "${Iris_CI_GITURL}" "${Iris_CI_DIR}" "${Iris_SHA}"
 
 # Extract required version of std++
-stdpp_VERSION=$(grep -F coq-stdpp < "${Iris_CI_DIR}/opam" | grep -E 'dev\.([0-9a-z.-]+)' -o)
-stdpp_URL=$(opam show "coq-stdpp.$stdpp_VERSION" -f upstream-url)
-read -r -a stdpp_URL_PARTS <<< "$(echo "$stdpp_URL" | tr '#' ' ')"
+stdpp_SHA=$(grep -F coq-stdpp < "${Iris_CI_DIR}/opam" | sed 's/.*"dev\.[0-9.-]\+\.\([0-9a-z]\+\)".*/\1/')
 
 # Setup std++
-git_checkout "${stdpp_CI_BRANCH}" "${stdpp_CI_GITURL}" "${stdpp_CI_DIR}" "${stdpp_URL_PARTS[1]}"
+git_checkout "${stdpp_CI_BRANCH}" "${stdpp_CI_GITURL}" "${stdpp_CI_DIR}" "${stdpp_SHA}"
 
 # Build std++
 ( cd "${stdpp_CI_DIR}" && make && make install )