Index: sys/kern/kern_sysctl.c
===================================================================
--- sys/kern/kern_sysctl.c
+++ sys/kern/kern_sysctl.c
@@ -1997,12 +1997,11 @@
 	if (KTRPOINT(curthread, KTR_SYSCTL))
 		ktrsysctl(name, namelen);
 #endif
-
-	if (req.oldptr && req.oldlen > PAGE_SIZE) {
+	memlocked = 0;
+	if (req.oldptr && req.oldlen > 4 * PAGE_SIZE) {
 		memlocked = 1;
 		sx_xlock(&sysctlmemlock);
-	} else
-		memlocked = 0;
+	}
 	CURVNET_SET(TD_TO_VNET(td));
 
 	for (;;) {