diff --git a/lib/libthr/arch/amd64/include/pthread_md.h b/lib/libthr/arch/amd64/include/pthread_md.h
--- a/lib/libthr/arch/amd64/include/pthread_md.h
+++ b/lib/libthr/arch/amd64/include/pthread_md.h
@@ -47,8 +47,8 @@
 {
 	struct pthread *thr;
 
-	__asm __volatile("movq %%fs:%1, %0" : "=r" (thr)
-	    : "m" (*(volatile u_long *)offsetof(struct tcb, tcb_thread)));
+	__asm __volatile("movq %%fs:%c1, %0" : "=r" (thr)
+	    : "i" (offsetof(struct tcb, tcb_thread)));
 	return (thr);
 }