diff --git a/src/llama-kv-cache-unified.cpp b/src/llama-kv-cache-unified.cpp
index d8f4e7ffc..3566d5fd4 100644
--- a/src/llama-kv-cache-unified.cpp
+++ b/src/llama-kv-cache-unified.cpp
@@ -462,7 +462,7 @@ bool llama_kv_cache_unified::update(llama_context * lctx, bool do_shift, const d
             for (uint32_t i = 0; i < n_kv; ++i) {
                 assert(dinfo.ids[i] <= n_kv);
 
-                if (dinfo.ids[i] == n_kv) {
+                if (dinfo.ids[i] == n_kv || dinfo.ids[i] == i) {
                     continue;
                 }
 
diff --git a/src/llama-kv-cells.h b/src/llama-kv-cells.h
index d71853592..acf30aebe 100644
--- a/src/llama-kv-cells.h
+++ b/src/llama-kv-cells.h
@@ -80,6 +80,9 @@ public:
         assert(isrc < pos.size());
         assert(idst < pos.size());
 
+        assert(pos[idst] == -1);
+        assert(pos[isrc] != -1);
+
         pos  [idst] = pos  [isrc];
         shift[idst] = shift[isrc];
         seq  [idst] = seq  [isrc];