diff --git a/keyserver/bash/source-nvm.sh b/keyserver/bash/source-nvm.sh
--- a/keyserver/bash/source-nvm.sh
+++ b/keyserver/bash/source-nvm.sh
@@ -9,9 +9,9 @@
 [ -n "$IN_NIX_SHELL" ] && exit 0
 
 # Intel Mac
-[ -s "/usr/local/opt/nvm/nvm.sh" ] && . "/usr/local/opt/nvm/nvm.sh"
+[[ -s "/usr/local/opt/nvm/nvm.sh" ]] && . "/usr/local/opt/nvm/nvm.sh"
 # ARM-based Mac
-[ -s "/opt/homebrew/opt/nvm/nvm.sh" ] && . "/opt/homebrew/opt/nvm/nvm.sh"
+[[ -s "/opt/homebrew/opt/nvm/nvm.sh" ]] && . "/opt/homebrew/opt/nvm/nvm.sh"
 # Ubuntu
-[ -s "$NVM_DIR/nvm.sh" ] && . "$NVM_DIR/nvm.sh"
+[[ -s "$NVM_DIR/nvm.sh" ]] && . "$NVM_DIR/nvm.sh"
 nvm install --no-progress