diff --git a/lib/command.js b/lib/command.js
index ab8887e857..859b006a06 100644
--- a/lib/command.js
+++ b/lib/command.js
@@ -11,7 +11,7 @@ const NO_ESCAPE_REGEXP = /^[\w.-]+$/;
 const DOUBLE_QUOTES_REGEXP = /"/g;
 
 const escapeArg = arg => {
-	if (NO_ESCAPE_REGEXP.test(arg)) {
+	if (typeof arg !== 'string' || NO_ESCAPE_REGEXP.test(arg)) {
 		return arg;
 	}