diff --git a/src/rk65c02.c b/src/rk65c02.c
index 5a7b041..c59f942 100644
--- a/src/rk65c02.c
+++ b/src/rk65c02.c
@@ -35,7 +35,8 @@ rk65c02_start(rk65c02emu_t *e) {
 		if (id.emul != NULL)
 			id.emul(e, &i);
 		else {
-			printf("unimplemented opcode %X\n", i.opcode);
+			printf("unimplemented opcode %X @ %X\n", i.opcode,
+			    e->regs.PC);
 			e->state = STOPPED;
 		}