diff --git a/shell/ql.sh b/shell/ql.sh
index 24e7b87f..8497e27a 100755
--- a/shell/ql.sh
+++ b/shell/ql.sh
@@ -1,4 +1,9 @@
 #!/usr/bin/env bash
 
+if [[ -z "$QL_DIR" ]]; then
+  echo "Error: QL_DIR environment variable is not set"
+  exit 1
+fi
+
 dir_shell=$QL_DIR/shell
 . $dir_shell/update.sh "$@"