diff --git a/lib/kill.js b/lib/kill.js
index dc1c77c38..813cf2e08 100644
--- a/lib/kill.js
+++ b/lib/kill.js
@@ -18,9 +18,14 @@ const setKillTimeout = (kill, signal, options, killResult) => {
 	}
 
 	const timeout = getForceKillAfterTimeout(options);
-	setTimeout(() => {
+	const t = setTimeout(() => {
 		kill('SIGKILL');
-	}, timeout).unref();
+	}, timeout);
+
+	// istanbul ignore else
+	if (t.unref) {
+		t.unref();
+	}
 };
 
 const shouldForceKill = (signal, {forceKillAfterTimeout}, killResult) => {