diff --git a/Makefile b/Makefile
index 697527326e3a02f512480a65198d31d85e9de020..28dbbfdd12e82151bbea5e1229262cca1125a29c 100644
--- a/Makefile
+++ b/Makefile
@@ -51,7 +51,7 @@ else
 	PLATFORM_CCFLAGS += $(JEMALLOC_INCLUDE) -DHAVE_JEMALLOC
 endif
 
-WARNING_FLAGS = -Wall -Werror -Wno-sign-compare
+WARNING_FLAGS = -Wall -Werror
 CFLAGS += $(WARNING_FLAGS) -I. -I./include $(PLATFORM_CCFLAGS) $(OPT)
 CXXFLAGS += $(WARNING_FLAGS) -I. -I./include $(PLATFORM_CXXFLAGS) $(OPT) -Woverloaded-virtual
 
diff --git a/db/column_family_test.cc b/db/column_family_test.cc
index 168549d0c66f5e8c73567add01f9b9319c4a0bdd..f21bea481a18d2e2ca1a28dad94202b415f68bde 100644
--- a/db/column_family_test.cc
+++ b/db/column_family_test.cc
@@ -922,7 +922,7 @@ TEST(ColumnFamilyTest, DontRollEmptyLogs) {
   Open();
   CreateColumnFamiliesAndReopen({"one", "two", "three", "four"});
 
-  for (int i = 0; i < handles_.size(); ++i) {
+  for (size_t i = 0; i < handles_.size(); ++i) {
     PutRandomData(i, 10, 100);
   }
   int num_writable_file_start = env_->GetNumberOfNewWritableFileCalls();
diff --git a/db/db_bench.cc b/db/db_bench.cc
index 345821596761e843e613b6660fc6cc0c88ce7b9e..04328227730e60deedbe8058edee3bc4db7970ed 100644
--- a/db/db_bench.cc
+++ b/db/db_bench.cc
@@ -1685,7 +1685,7 @@ class Benchmark {
       OpenDb(options, FLAGS_db, &db_);
     } else {
       multi_dbs_.clear();
-      for (size_t i = 0; i < FLAGS_num_multi_db; i++) {
+      for (int i = 0; i < FLAGS_num_multi_db; i++) {
         DB* db;
         OpenDb(options, GetDbNameForMultiple(FLAGS_db, i), &db);
         multi_dbs_.push_back(db);
@@ -1910,7 +1910,7 @@ class Benchmark {
     ReadOptions options(FLAGS_verify_checksum, true);
     std::vector<Slice> keys;
     std::vector<std::string> values(entries_per_batch_);
-    while (keys.size() < entries_per_batch_) {
+    while (static_cast<int64_t>(keys.size()) < entries_per_batch_) {
       keys.push_back(AllocateKey());
     }
 
@@ -1922,7 +1922,7 @@ class Benchmark {
             FLAGS_num, &keys[i]);
       }
       std::vector<Status> statuses = db->MultiGet(options, keys, &values);
-      assert(statuses.size() == entries_per_batch_);
+      assert(static_cast<int64_t>(statuses.size()) == entries_per_batch_);
 
       read += entries_per_batch_;
       for (int64_t i = 0; i < entries_per_batch_; ++i) {
diff --git a/db/file_indexer_test.cc b/db/file_indexer_test.cc
index 26a0508a390854efeab81f0ccb008b67c4636fdb..bfec8dd8f62b6f8d537f316ace5e8bf31b557f4b 100644
--- a/db/file_indexer_test.cc
+++ b/db/file_indexer_test.cc
@@ -60,7 +60,7 @@ struct FileIndexerTest {
   }
 
   void Reset() {
-    for (int i = 0; i < kNumLevels; ++i) {
+    for (uint32_t i = 0; i < kNumLevels; ++i) {
       for (auto* f : files[i]) {
         delete f;
       }
diff --git a/util/benchharness.cc b/util/benchharness.cc
index af612316e731fe22c148d35be183ca2bdceb8207..8cd37007b44268cbda6d635668b68614b45ef8c3 100644
--- a/util/benchharness.cc
+++ b/util/benchharness.cc
@@ -305,7 +305,7 @@ static void PrintBenchmarkResultsAsTable(
 
   // Compute the longest benchmark name
   size_t longestName = 0;
-  for (auto i = 1; i < benchmarks.size(); i++) {
+  for (size_t i = 1; i < benchmarks.size(); i++) {
     longestName = max(longestName, strlen(get<1>(benchmarks[i])));
   }
 
@@ -379,7 +379,7 @@ void RunBenchmarks() {
 
   auto const globalBaseline = RunBenchmarkGetNSPerIteration(
     get<2>(benchmarks.front()), 0);
-  for (auto i = 1; i < benchmarks.size(); i++) {
+  for (size_t i = 1; i < benchmarks.size(); i++) {
     double elapsed = 0.0;
     if (strcmp(get<1>(benchmarks[i]), "-") != 0) {  // skip separators
       elapsed = RunBenchmarkGetNSPerIteration(get<2>(benchmarks[i]),