diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9cc6de3..fc87578 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -52,8 +52,10 @@ add_test(NAME conflict_set_cxx_api_test COMMAND conflict_set_cxx_api_test)
 target_compile_options(conflict_set_cxx_api_test PRIVATE -Wall -Wextra -Wpedantic -Wunreachable-code -Werror)
 
 # fuzz test
+set(FUZZ_FLAGS "-fsanitize=fuzzer,address,undefined")
 include(CheckCXXCompilerFlag)
-check_cxx_compiler_flag(HAS_LIB_FUZZER -fsanitize=fuzzer)
+set(CMAKE_REQUIRED_LINK_OPTIONS ${FUZZ_FLAGS})
+check_cxx_compiler_flag(${FUZZ_FLAGS} HAS_LIB_FUZZER)
 
 if (HAS_LIB_FUZZER)
   add_executable(conflict_set_fuzz_test ConflictSet.cpp ConflictSet.h)
@@ -61,6 +63,6 @@ if (HAS_LIB_FUZZER)
   # keep asserts for test
   target_compile_options(conflict_set_fuzz_test PRIVATE -UNDEBUG)
   target_compile_options(conflict_set_fuzz_test PRIVATE -Wall -Wextra -Wpedantic -Wunreachable-code)
-  target_compile_options(conflict_set_fuzz_test PRIVATE -fsanitize=fuzzer)
-  target_link_options(conflict_set_fuzz_test PRIVATE -fsanitize=fuzzer)
+  target_compile_options(conflict_set_fuzz_test PRIVATE ${FUZZ_FLAGS})
+  target_link_options(conflict_set_fuzz_test PRIVATE ${FUZZ_FLAGS})
 endif()
diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index e30f337..03eb792 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -908,21 +908,38 @@ struct __attribute__((__visibility__("hidden"))) ConflictSet::Impl {
   }
 
   void check(const ReadRange *reads, Result *results, int count) const {
-    Arena arena;
-    auto *iters = new (arena) Iterator[count];
-    auto *begins = new (arena) Key[count];
+    int searchCount = 0;
     for (int i = 0; i < count; ++i) {
-      begins[i] = reads[i].begin;
+      if (reads[i].readVersion >= oldestVersion) {
+        ++searchCount;
+      } else {
+        results[i] = ConflictSet::TooOld;
+      }
     }
-    lastLeqMulti(arena, root, std::span<Key>(begins, count), iters);
-    // TODO check non-singleton reads lol
+    Arena arena;
+    auto *iters = new (arena) Iterator[searchCount];
+    auto *begins = new (arena) Key[searchCount];
+    int j = 0;
     for (int i = 0; i < count; ++i) {
-      assert(reads[i].end.len == 0);
-      assert(iters[i].node != nullptr);
-      if ((iters[i].cmp == 0
-               ? iters[i].node->pointVersion
-               : iters[i].node->rangeVersion) > reads[i].readVersion) {
-        results[i] = ConflictSet::Conflict;
+      if (reads[i].readVersion >= oldestVersion) {
+        begins[j++] = reads[i].begin;
+      }
+    }
+    lastLeqMulti(arena, root, std::span<Key>(begins, searchCount), iters);
+    // TODO check non-singleton reads lol
+    j = 0;
+    for (int i = 0; i < count; ++i) {
+      if (reads[i].readVersion >= oldestVersion) {
+        assert(reads[i].end.len == 0);
+        assert(iters[i].node != nullptr);
+        if ((iters[j].cmp == 0
+                 ? iters[j].node->pointVersion
+                 : iters[j].node->rangeVersion) > reads[i].readVersion) {
+          results[i] = ConflictSet::Conflict;
+        } else {
+          results[i] = ConflictSet::Commit;
+        }
+        ++j;
       }
     }
   }
@@ -1226,25 +1243,60 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
 
   while (gArbitrary.hasEntropy()) {
     Arena arena;
-    int numWrites = gArbitrary.bounded(10);
-    int64_t v = ++writeVersion;
-    auto *writes = new (arena) ConflictSet::WriteRange[numWrites];
-    std::set<int> keys;
-    while (int(keys.size()) < numWrites) {
-      keys.insert(gRandom.bounded(100));
+    {
+      int numWrites = gArbitrary.bounded(10);
+      int64_t v = ++writeVersion;
+      auto *writes = new (arena) ConflictSet::WriteRange[numWrites];
+      std::set<int, std::less<int>, ArenaAlloc<int>> keys{
+          ArenaAlloc<int>(&arena)};
+      while (int(keys.size()) < numWrites) {
+        keys.insert(gRandom.bounded(100));
+      }
+      auto iter = keys.begin();
+      for (int i = 0; i < numWrites; ++i) {
+        writes[i].begin = toKey(arena, *iter++);
+        writes[i].end.len = 0;
+        writes[i].writeVersion = v;
+      }
+      cs.addWrites(writes, numWrites);
+      refImpl.addWrites(writes, numWrites);
     }
-    auto iter = keys.begin();
-    for (int i = 0; i < numWrites; ++i) {
-      writes[i].begin = toKey(arena, *iter++);
-      writes[i].end.len = 0;
-      writes[i].writeVersion = v;
-    }
-    cs.addWrites(writes, numWrites);
-    refImpl.addWrites(writes, numWrites);
     bool success = checkCorrectness(cs.root, refImpl);
     if (!success) {
       abort();
     }
+    {
+      int numReads = gArbitrary.bounded(10);
+      int64_t v = writeVersion - gArbitrary.bounded(10);
+      auto *reads = new (arena) ConflictSet::ReadRange[numReads];
+      std::set<int, std::less<int>, ArenaAlloc<int>> keys{
+          ArenaAlloc<int>(&arena)};
+      while (int(keys.size()) < numReads) {
+        keys.insert(gRandom.bounded(100));
+      }
+      auto iter = keys.begin();
+      for (int i = 0; i < numReads; ++i) {
+        reads[i].begin = toKey(arena, *iter++);
+        reads[i].end.len = 0;
+        reads[i].readVersion = v;
+      }
+      auto *results1 = new (arena) ConflictSet::Result[numReads];
+      auto *results2 = new (arena) ConflictSet::Result[numReads];
+      cs.check(reads, results1, numReads);
+      refImpl.check(reads, results2, numReads);
+      for (int i = 0; i < numReads; ++i) {
+        if (results1[i] != results2[i]) {
+          fprintf(stderr,
+                  "Expected %d, got %d for read of %.*s at version %d\n",
+                  results2[i], results1[i], reads[i].begin.len,
+                  reads[i].begin.p, int(reads[i].readVersion));
+          std::string referenceLogicalMap;
+          refImpl.printLogical(referenceLogicalMap);
+          fprintf(stderr, "Logical map:\n\n%s\n", referenceLogicalMap.c_str());
+          abort();
+        }
+      }
+    }
   }
   return 0;
 }