diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 55a59d889dbd..0b5e2b546566 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -847,12 +847,15 @@ static int __init parse_memopt(char *p)
 	if (!p)
 		return -EINVAL;
 
-#ifdef CONFIG_X86_32
 	if (!strcmp(p, "nopentium")) {
+#ifdef CONFIG_X86_32
 		setup_clear_cpu_cap(X86_FEATURE_PSE);
 		return 0;
-	}
+#else
+		printk(KERN_WARNING "mem=nopentium ignored! (only supported on x86_32)\n");
+		return -EINVAL;
 #endif
+	}
 
 	userdef = 1;
 	mem_size = memparse(p, &p);