Index: sys/arm64/arm64/machdep.c
===================================================================
--- sys/arm64/arm64/machdep.c
+++ sys/arm64/arm64/machdep.c
@@ -429,6 +429,7 @@
 	mcp->mc_gpregs.gp_sp = tf->tf_sp;
 	mcp->mc_gpregs.gp_lr = tf->tf_lr;
 	mcp->mc_gpregs.gp_elr = tf->tf_elr;
+	mcp->mc_gpregs.gp_esr = tf->tf_esr;
 
 	return (0);
 }
@@ -449,6 +450,7 @@
 	tf->tf_sp = mcp->mc_gpregs.gp_sp;
 	tf->tf_lr = mcp->mc_gpregs.gp_lr;
 	tf->tf_elr = mcp->mc_gpregs.gp_elr;
+	tf->tf_esr = mcp->mc_gpregs.gp_esr;
 	tf->tf_spsr = mcp->mc_gpregs.gp_spsr;
 
 	return (0);
Index: sys/arm64/include/ucontext.h
===================================================================
--- sys/arm64/include/ucontext.h
+++ sys/arm64/include/ucontext.h
@@ -39,6 +39,7 @@
 	__register_t	gp_sp;
 	__register_t	gp_elr;
 	__uint32_t	gp_spsr;
+	__register_t	gp_esr;
 	int		gp_pad;
 };