diff --git a/shell.nix b/shell.nix
index b7edf8725..c2fc68b95 100644
--- a/shell.nix
+++ b/shell.nix
@@ -88,7 +88,7 @@ let
         set +xe
       fi
 
-      if [[ -z "MEMCACHED_HOST" ]]; then
+      if [[ -z "$MEMCACHED_HOST" ]]; then
         set -xe
 
         memcached -l localhost -p 11213 &>/dev/null &