diff --git a/agent_based_epidemic_sim/agent_synthesis/agent_sampler.cc b/agent_based_epidemic_sim/agent_synthesis/agent_sampler.cc
index 24d896be..bfdaeb53 100644
--- a/agent_based_epidemic_sim/agent_synthesis/agent_sampler.cc
+++ b/agent_based_epidemic_sim/agent_synthesis/agent_sampler.cc
@@ -16,7 +16,7 @@
 
 namespace abesim {
 namespace {
-constexpr int64 kPopulationProfileId = 0;
+constexpr int64_t kPopulationProfileId = 0;
 }  // namespace
 
 AgentProto ShuffledLocationAgentSampler::Next() {
diff --git a/agent_based_epidemic_sim/agent_synthesis/shuffled_sampler.cc b/agent_based_epidemic_sim/agent_synthesis/shuffled_sampler.cc
index ddb81213..4984af22 100644
--- a/agent_based_epidemic_sim/agent_synthesis/shuffled_sampler.cc
+++ b/agent_based_epidemic_sim/agent_synthesis/shuffled_sampler.cc
@@ -21,7 +21,7 @@
 namespace abesim {
 
 ShuffledSampler::ShuffledSampler(
-    const absl::flat_hash_map<int64, int>& uuids_to_sizes) {
+    const absl::flat_hash_map<int64_t, int>& uuids_to_sizes) {
   for (auto key_val : uuids_to_sizes) {
     for (int i = 0; i < key_val.second; ++i) {
       slots_.push_back(key_val.first);
@@ -30,25 +30,25 @@ ShuffledSampler::ShuffledSampler(
   std::shuffle(slots_.begin(), slots_.end(), GetBitGen());
 }
 
-int64 ShuffledSampler::Next() {
+int64_t ShuffledSampler::Next() {
   DCHECK(i_ < slots_.size());
   return slots_[i_++];
 }
 
 std::unique_ptr<ShuffledSampler> MakeBusinessSampler(
-    const GammaDistribution& business_distribution, const int64 population_size,
-    const UuidGenerator& uuid_generator,
+    const GammaDistribution& business_distribution,
+    const int64_t population_size, const UuidGenerator& uuid_generator,
     std::vector<LocationProto>* locations) {
   auto business_size_distribution = std::gamma_distribution<float>(
       business_distribution.alpha(), business_distribution.beta());
   std::mt19937 rng;
-  absl::flat_hash_map<int64, int> uuid_to_sizes;
+  absl::flat_hash_map<int64_t, int> uuid_to_sizes;
   for (int population = 0; population < population_size;) {
     LocationProto location;
     location.mutable_reference()->set_uuid(uuid_generator.GenerateUuid());
     location.mutable_reference()->set_type(LocationReference::BUSINESS);
     const int size =
-        std::min(static_cast<int64>(business_size_distribution(rng)),
+        std::min(static_cast<int64_t>(business_size_distribution(rng)),
                  population_size - population);
     location.mutable_dense()->set_size(size);
     locations->push_back(location);
@@ -61,11 +61,11 @@ std::unique_ptr<ShuffledSampler> MakeBusinessSampler(
 
 std::unique_ptr<ShuffledSampler> MakeHouseholdSampler(
     const DiscreteDistribution& household_distribution,
-    const int64 population_size, const UuidGenerator& uuid_generator,
+    const int64_t population_size, const UuidGenerator& uuid_generator,
     std::vector<LocationProto>* locations) {
   auto household_size_sampler =
-      DiscreteDistributionSampler<int64>::FromProto(household_distribution);
-  absl::flat_hash_map<int64, int> uuid_to_sizes;
+      DiscreteDistributionSampler<int64_t>::FromProto(household_distribution);
+  absl::flat_hash_map<int64_t, int> uuid_to_sizes;
   for (int population = 0; population < population_size;) {
     LocationProto location;
     location.mutable_reference()->set_uuid(uuid_generator.GenerateUuid());