diff --git a/parsec/include/parsec/sys/atomic-x86_64.h b/parsec/include/parsec/sys/atomic-x86_64.h
index a141e7a26..782904d58 100644
--- a/parsec/include/parsec/sys/atomic-x86_64.h
+++ b/parsec/include/parsec/sys/atomic-x86_64.h
@@ -196,7 +196,7 @@ __int128_t parsec_atomic_fetch_add_int128(volatile __int128_t* v, __int128_t i)
     do {
         ov = *v;
         nv = ov + i;
-    } while( !parsec_atomic_cas_int128(v, nv) );
+    } while( !parsec_atomic_cas_int128(v, ov, nv) );
     return ov;
 }
 #endif