diff --git a/src/x86_64/Gtrace.c b/src/x86_64/Gtrace.c
index 656b6dc6..72b08e63 100644
--- a/src/x86_64/Gtrace.c
+++ b/src/x86_64/Gtrace.c
@@ -157,6 +157,7 @@ trace_cache_expand (unw_trace_cache_t *cache)
   Debug(5, "expanded cache from 2^%lu to 2^%lu hash bucket sets\n",
 	cache->log_frame_vecs, new_size);
   cache->log_frame_vecs = new_size;
+  cache->used = 0;
   return 0;
 }