diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index 6ce3d8a..c11ee2c 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -3060,9 +3060,18 @@ Node *firstGeqPhysical(Node *n, const std::span<const uint8_t> key) {
   }
 }
 
+thread_local double accume_point_read = 0;
+thread_local double accume_prefix_read = 0;
+thread_local double accume_range_read = 0;
+thread_local double accume_max_between = 0;
+
 struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
 
   void check(const ReadRange *reads, Result *result, int count) {
+    assert(accume_point_read == 0);
+    assert(accume_prefix_read == 0);
+    assert(accume_range_read == 0);
+    assert(accume_max_between == 0);
     for (int i = 0; i < count; ++i) {
       const auto &r = reads[i];
       auto begin = std::span<const uint8_t>(r.begin.p, r.begin.len);
@@ -3303,13 +3312,9 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
   COUNTER(node256_released_total,
           "Total number of nodes of type \"Node256\" that have been released");
   GAUGE(memory_bytes, "Total number of bytes in use.");
-  double accume_point_read = 0;
   COUNTER(read_point_total, "Total number of point reads checked.");
-  double accume_prefix_read = 0;
   COUNTER(read_prefix_total, "Total number of prefix reads checked.");
-  double accume_range_read = 0;
   COUNTER(read_range_total, "Total number of range reads checked.");
-  double accume_max_between = 0;
   COUNTER(read_range_node_total,
           "Total number of range checks of individual nodes while "
           "checking a range read.");