diff --git a/unittest/apiexample_test.cc b/unittest/apiexample_test.cc
index fe514de4..275eb1da 100644
--- a/unittest/apiexample_test.cc
+++ b/unittest/apiexample_test.cc
@@ -32,10 +32,10 @@ namespace {
 class QuickTest : public testing::Test {
  protected:
   virtual void SetUp() {
-    start_time_ = time(NULL);
+    start_time_ = time(nullptr);
   }
   virtual void TearDown() {
-    const time_t end_time = time(NULL);
+    const time_t end_time = time(nullptr);
     EXPECT_TRUE(end_time - start_time_ <=25) << "The test took too long - " << ::testing::PrintToString(end_time - start_time_);
   }
   time_t start_time_;
diff --git a/unittest/unicharcompress_test.cc b/unittest/unicharcompress_test.cc
index d67837be..4f97ca3b 100644
--- a/unittest/unicharcompress_test.cc
+++ b/unittest/unicharcompress_test.cc
@@ -135,7 +135,7 @@ class UnicharcompressTest : public ::testing::Test {
     RecodedCharID extended = code;
     int length = code.length();
     const GenericVector<int>* final_codes = compressed_.GetFinalCodes(code);
-    if (final_codes != NULL) {
+    if (final_codes != nullptr) {
       for (int i = 0; i < final_codes->size(); ++i) {
         int ending = (*final_codes)[i];
         EXPECT_GT(times_seen[ending](length), 0);
@@ -145,7 +145,7 @@ class UnicharcompressTest : public ::testing::Test {
       }
     }
     const GenericVector<int>* next_codes = compressed_.GetNextCodes(code);
-    if (next_codes != NULL) {
+    if (next_codes != nullptr) {
       for (int i = 0; i < next_codes->size(); ++i) {
         int extension = (*next_codes)[i];
         EXPECT_GT(times_seen[extension](length), 0);