diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index ba370dc8685bf8f9bf31e9100f78c4e800ea755e..58325a6604a4fa650952bf49323abbb82e5007e5 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -164,6 +164,9 @@ void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
 
 static int __init idle_setup(char *str)
 {
+	if (!str)
+		return -EINVAL;
+
 	if (!strcmp(str, "poll")) {
 		printk("using polling idle threads.\n");
 		pm_idle = poll_idle;