diff --git a/plugins/ralph-loop/scripts/setup-ralph-loop.sh b/plugins/ralph-loop/scripts/setup-ralph-loop.sh
index 3d41db4..d8906f2 100755
--- a/plugins/ralph-loop/scripts/setup-ralph-loop.sh
+++ b/plugins/ralph-loop/scripts/setup-ralph-loop.sh
@@ -110,7 +110,7 @@ HELP_EOF
 done
 
 # Join all prompt parts with spaces
-PROMPT="${PROMPT_PARTS[*]}"
+PROMPT="${PROMPT_PARTS[*]:-}"
 
 # Validate prompt is non-empty
 if [[ -z "$PROMPT" ]]; then