diff --git a/maintainer/pineappl-ci/script.sh b/maintainer/pineappl-ci/script.sh
index 304cdc6c..cce9c98b 100755
--- a/maintainer/pineappl-ci/script.sh
+++ b/maintainer/pineappl-ci/script.sh
@@ -21,7 +21,7 @@ done
 yum -y install perl-IPC-Cmd
 
 # install cargo-c needed for the CAPI
-cargo install cargo-c --version ${CARGOC_V} --features=vendored-openssl
+cargo install --locked cargo-c --version ${CARGOC_V} --features=vendored-openssl
 
 # remove files generated by cargo
 rm -r /usr/local/cargo/registry