diff --git a/src/pretty.ts b/src/pretty.ts
index c7399cd..b9eab69 100644
--- a/src/pretty.ts
+++ b/src/pretty.ts
@@ -40,7 +40,7 @@ export const prettyOptsFactory = (opts: PrettyOptionsExtra = {}): PrettyOptions
         messageFormat: (log, messageKey, levelLabel, {colors}) => {
             const labels: string[] = log.labels as string[] ?? [];
             const labelContent = labels.length === 0 ? '' : `${labels.map((x: string) => colors.blackBright(`[${x}]`)).join(' ')} `;
-            const msg = redactFunc((log[messageKey] as string));
+            const msg = redactFunc((log[messageKey] as string) ?? '');
             let stackTrace = log.err !== undefined ? redactFunc(`\n${(log.err as any).stack}`) : '';
             stackTrace = stackTrace.replaceAll(/^\s+at\s.+$/gm, (match) => `${colors.blackBright(match)}`) //$&
             return `${labelContent}${msg}${stackTrace}`;