diff --git a/tools/db_stress.cc b/tools/db_stress.cc
index e4aa85e0d..da2a122d4 100644
--- a/tools/db_stress.cc
+++ b/tools/db_stress.cc
@@ -2372,6 +2372,11 @@ class StressTest {
       }
 #endif
     }
+    while (!thread->snapshot_queue.empty()) {
+      db_->ReleaseSnapshot(thread->snapshot_queue.front().second.snapshot);
+      delete thread->snapshot_queue.front().second.key_vec;
+      thread->snapshot_queue.pop();
+    }
 
     thread->stats.Stop();
   }
@@ -2486,8 +2491,7 @@ class StressTest {
       ReadOptions cmp_ro;
       cmp_ro.snapshot = snapshot;
       cmp_ro.total_order_seek = true;
-      std::unique_ptr<Iterator> cmp_iter(
-          db_->NewIterator(readoptionscopy, cfh));
+      std::unique_ptr<Iterator> cmp_iter(db_->NewIterator(cmp_ro, cfh));
       bool diverged = false;
 
       iter->Seek(key);
@@ -2539,12 +2543,27 @@ class StressTest {
       return;
     }
 
+    if (ro.iterate_lower_bound != nullptr) {
+      // Lower bound would create a lot of discrepency for now so disabling
+      // the verification for now.
+      *diverged = true;
+      return;
+    }
+
     if (iter->Valid() && !cmp_iter->Valid()) {
       fprintf(stderr,
-              "Control interator is invalid but iterator has value %s seek key "
+              "Control interator is invalid but iterator has key %s seek key "
               "%s\n",
               iter->key().ToString(true).c_str(),
               seek_key.ToString(true).c_str());
+      if (ro.iterate_upper_bound != nullptr) {
+        fprintf(stderr, "upper bound %s\n",
+                ro.iterate_upper_bound->ToString(true).c_str());
+      }
+      if (ro.iterate_lower_bound != nullptr) {
+        fprintf(stderr, "lower bound %s\n",
+                ro.iterate_lower_bound->ToString(true).c_str());
+      }
 
       *diverged = true;
     } else if (cmp_iter->Valid()) {
@@ -2582,8 +2601,8 @@ class StressTest {
       }
       // Check upper or lower bounds.
       if (!*diverged) {
-        if (!iter->Valid() ||
-            (iter->key() != cmp_iter->key() &&
+        if ((iter->Valid() && iter->key() != cmp_iter->key()) ||
+            (!iter->Valid() &&
              (ro.iterate_upper_bound == nullptr ||
               cmp->Compare(total_order_key, *ro.iterate_upper_bound) < 0) &&
              (ro.iterate_lower_bound == nullptr ||
@@ -3280,6 +3299,8 @@ class NonBatchedOpsStressTest : public StressTest {
     const int64_t keys_per_thread = max_key / shared->GetNumThreads();
     int64_t start = keys_per_thread * thread->tid;
     int64_t end = start + keys_per_thread;
+    uint64_t prefix_to_use =
+        (FLAGS_prefix_size < 0) ? 1 : static_cast<size_t>(FLAGS_prefix_size);
     if (thread->tid == shared->GetNumThreads() - 1) {
       end = max_key;
     }
@@ -3298,8 +3319,7 @@ class NonBatchedOpsStressTest : public StressTest {
           }
           // TODO(ljin): update "long" to uint64_t
           // Reseek when the prefix changes
-          if (i % (static_cast<int64_t>(1) << 8 * (8 - FLAGS_prefix_size)) ==
-              0) {
+          if (i % (static_cast<int64_t>(1) << 8 * (8 - prefix_to_use)) == 0) {
             iter->Seek(Key(i));
           }
           std::string from_db;
@@ -4042,6 +4062,8 @@ class BatchedOpsStressTest : public StressTest {
   virtual Status TestPrefixScan(ThreadState* thread, const ReadOptions& readoptions,
       const std::vector<int>& rand_column_families,
       const std::vector<int64_t>& rand_keys) {
+    size_t prefix_to_use =
+        (FLAGS_prefix_size < 0) ? 7 : static_cast<size_t>(FLAGS_prefix_size);
     std::string key_str = Key(rand_keys[0]);
     Slice key = key_str;
     auto cfh = column_families_[rand_column_families[0]];
@@ -4056,7 +4078,7 @@ class BatchedOpsStressTest : public StressTest {
     Status s = Status::OK();
     for (int i = 0; i < 10; i++) {
       prefixes[i] += key.ToString();
-      prefixes[i].resize(FLAGS_prefix_size);
+      prefixes[i].resize(prefix_to_use);
       prefix_slices[i] = Slice(prefixes[i]);
       readoptionscopy[i] = readoptions;
       readoptionscopy[i].snapshot = snapshot;