Index: sys/riscv/riscv/trap.c
===================================================================
--- sys/riscv/riscv/trap.c
+++ sys/riscv/riscv/trap.c
@@ -163,7 +163,9 @@
 	struct thread *td;
 
 	td = curthread;
-	td->td_frame = frame;
+
+	KASSERT(td->td_frame == frame,
+	    ("%s: td_frame %p != frame %p", __func__, td->td_frame, frame));
 
 	syscallenter(td);
 	syscallret(td);