diff --git a/spectre-meltdown-checker.sh b/spectre-meltdown-checker.sh
index d802bfb..7272ba8 100755
--- a/spectre-meltdown-checker.sh
+++ b/spectre-meltdown-checker.sh
@@ -1017,7 +1017,8 @@ pvulnstatus()
 					OK)   is_vuln="false";;
 					*)    echo "$0: error: unknown status '$2' passed to pvulnstatus()" >&2; exit 255;;
 				esac
-				json_output="${json_output:-[}{\"NAME\":\"$aka\",\"CVE\":\"$1\",\"VULNERABLE\":$is_vuln,\"INFOS\":\"$3\"},"
+				[ -z "$json_output" ] && json_output='['
+				json_output="${json_output}{\"NAME\":\"$aka\",\"CVE\":\"$1\",\"VULNERABLE\":$is_vuln,\"INFOS\":\"$3\"},"
 				;;
 
 			nrpe)	[ "$2" = VULN ] && nrpe_vuln="$nrpe_vuln $1";;