1 files changed, 2 insertions, 2 deletions

diff --git a/isa/decode.cpp b/isa/decode.cpp
index c35118b..af38c64 100644
--- a/isa/decode.cpp
+++ b/isa/decode.cpp
@@ -34,8 +34,8 @@ instruction_context decode(unsigned int dfifb, unsigned int pc, unsigned int bit
             inst.need_write_acc = true;
             inst.need_write_link = true;
             inst.ef = [](auto &ctx) {
-                unsigned int sum = (ctx.link.value() << 12) + ctx.acc.value() + ctx.data.value();
-                ctx.link = (sum >> 12) & 1;
+                unsigned int sum = ctx.acc.value() + ctx.data.value();
+                ctx.link = ctx.link.value() ^ (sum >> 12);
                 ctx.acc = sum & 07777;
             };
             break;