diff --git a/sys/arm64/arm64/ptrace_machdep.c b/sys/arm64/arm64/ptrace_machdep.c
--- a/sys/arm64/arm64/ptrace_machdep.c
+++ b/sys/arm64/arm64/ptrace_machdep.c
@@ -113,7 +113,7 @@
 
 		KASSERT(*sizep == sizeof(uint32_t),
 		    ("%s: invalid size", __func__));
-		tp = (uint32_t)td->td_pcb->pcb_tpidr_el0;
+		tp = (uint32_t)td->td_pcb->pcb_tpidrro_el0;
 		memcpy(buf, &tp, sizeof(tp));
 	}
 	*sizep = sizeof(uint32_t);