diff --git a/changes/ticket40125 b/changes/ticket40125
new file mode 100644
index 0000000000..c68e3ce7b3
--- /dev/null
+++ b/changes/ticket40125
@@ -0,0 +1,4 @@
+  o Testing (onion service v2):
+    - Fix a rendezvous cache unit test that was triggering an underflow on the
+      global rend cache allocation. Fixes bug 40125; bugfix on
+      0.2.8.1-alpha.
diff --git a/src/test/test_rendcache.c b/src/test/test_rendcache.c
index cfeb640e02..de8c0aef41 100644
--- a/src/test/test_rendcache.c
+++ b/src/test/test_rendcache.c
@@ -974,11 +974,13 @@ test_rend_cache_entry_free(void *data)
 
   // Handles NULL descriptor correctly
   e = tor_malloc_zero(sizeof(rend_cache_entry_t));
+  rend_cache_increment_allocation(rend_cache_entry_allocation(e));
   rend_cache_entry_free(e);
 
   // Handles non-NULL descriptor correctly
   e = tor_malloc_zero(sizeof(rend_cache_entry_t));
   e->desc = tor_malloc(10);
+  rend_cache_increment_allocation(rend_cache_entry_allocation(e));
   rend_cache_entry_free(e);
 
  /* done: */