diff --git a/crates/xenia-cpu/src/disasm.rs b/crates/xenia-cpu/src/disasm.rs
index 5a98981..352219c 100644
--- a/crates/xenia-cpu/src/disasm.rs
+++ b/crates/xenia-cpu/src/disasm.rs
@@ -361,7 +361,15 @@ pub fn format(instr: &DecodedInstr) -> DisasmText {
         PpcOpcode::dcbz  => fmt_cache(instr, "dcbz"),
         PpcOpcode::dcbz128 => fmt_cache(instr, "dcbz128"),
         PpcOpcode::icbi  => fmt_cache(instr, "icbi"),
-        PpcOpcode::sync  => base("sync", String::new(), 0),
+        PpcOpcode::sync  => {
+            // L-field at PPC bit 10 (host bit 21) selects lwsync (L=1), the
+            // acquire barrier in every Xbox 360 spinlock. PPCBUG-641.
+            if (instr.raw >> 21) & 1 == 1 {
+                with_ext("sync", String::new(), 0, "lwsync", String::new(), 0)
+            } else {
+                base("sync", String::new(), 0)
+            }
+        }
         PpcOpcode::eieio => base("eieio", String::new(), 0),
         PpcOpcode::isync => base("isync", String::new(), 0),
 
diff --git a/crates/xenia-cpu/tests/golden/extended_mnemonics.json b/crates/xenia-cpu/tests/golden/extended_mnemonics.json
index 6749f94..0c442dd 100644
--- a/crates/xenia-cpu/tests/golden/extended_mnemonics.json
+++ b/crates/xenia-cpu/tests/golden/extended_mnemonics.json
@@ -525,7 +525,9 @@
       "raw": "0x7C2004AC",
       "addr": "0x82000000",
       "mnemonic": "sync",
-      "operands": ""
+      "operands": "",
+      "ext_mnemonic": "lwsync",
+      "ext_operands": ""
     },
     {
       "label": "trap",