diff --git a/nvm.sh b/nvm.sh
index 1b23698..8c94401 100644
--- a/nvm.sh
+++ b/nvm.sh
@@ -3419,7 +3419,7 @@ nvm() {
         esac
         shift
       done
-      case "${PATTERN}" in
+      case "${PATTERN-}" in
         'lts/*')
           NVM_LTS='*'
           unset PATTERN