diff --git a/ci-image/entrypoint.sh b/ci-image/entrypoint.sh
old mode 100644
new mode 100755
index 18077a8..27c6ec9
--- a/ci-image/entrypoint.sh
+++ b/ci-image/entrypoint.sh
@@ -3,5 +3,7 @@ set -e
 
 cd "$CI_PROJECT_DIR"
 
-echo "Activating flake's CI shell..."
-nix develop .#ci --impure --command "bash"
+nix_shell="${NIX_CI_SHELL:-ci}"
+
+echo "Activating flake's '$nix_shell' shell..."
+nix develop .#"$nix_shell" --impure --command "bash"