diff --git a/lib/libthr/thread/thr_attr.c b/lib/libthr/thread/thr_attr.c
index c2969e7cc564..0cac528a150d 100644
--- a/lib/libthr/thread/thr_attr.c
+++ b/lib/libthr/thread/thr_attr.c
@@ -569,14 +569,11 @@ _get_kern_cpuset_size(void)
 
 	if (kern_cpuset_size == 0) {
 		size_t len;
-		int maxcpus;
 
-		len = sizeof(maxcpus);
-		if (sysctlbyname("kern.smp.maxcpus", &maxcpus, &len, NULL, 0))
-			PANIC("failed to get sysctl kern.smp.maxcpus");
-		int nbits_long = sizeof(long) * NBBY;
-		int num_long = (maxcpus + nbits_long - 1) / nbits_long;
-		kern_cpuset_size = num_long * sizeof(long);
+		len = sizeof(kern_cpuset_size);
+		if (sysctlbyname("kern.sched.cpusetsize", &kern_cpuset_size,
+		    &len, NULL, 0))
+			PANIC("failed to get sysctl kern.sched.cpusetsize");
 	}
 
 	return (kern_cpuset_size);