diff --git a/payload_generator/ab_generator_unittest.cc b/payload_generator/ab_generator_unittest.cc
index 84eeb77..e00e6bd 100644
--- a/payload_generator/ab_generator_unittest.cc
+++ b/payload_generator/ab_generator_unittest.cc
@@ -65,9 +65,9 @@
     test_utils::FillWithData(&part_data);
   } else {
     std::mt19937 gen(12345);
-    std::uniform_int_distribution<uint8_t> dis(0, 255);
+    std::uniform_int_distribution<uint16_t> dis(0, 255);
     for (uint32_t i = 0; i < part_size; i++)
-      part_data.push_back(dis(gen));
+      part_data.push_back(static_cast<uint8_t>(dis(gen)));
   }
   ASSERT_EQ(part_size, part_data.size());
   ScopedTempFile part_file("SplitReplaceOrReplaceXzTest_part.XXXXXX");
@@ -213,9 +213,9 @@
     test_utils::FillWithData(&part_data);
   } else {
     std::mt19937 gen(12345);
-    std::uniform_int_distribution<uint8_t> dis(0, 255);
+    std::uniform_int_distribution<uint16_t> dis(0, 255);
     for (uint32_t i = 0; i < part_size; i++)
-      part_data.push_back(dis(gen));
+      part_data.push_back(static_cast<uint8_t>(dis(gen)));
   }
   ASSERT_EQ(part_size, part_data.size());
   ScopedTempFile part_file("MergeReplaceOrReplaceXzTest_part.XXXXXX");
diff --git a/payload_generator/delta_diff_utils_unittest.cc b/payload_generator/delta_diff_utils_unittest.cc
index 7348d74..b698339 100644
--- a/payload_generator/delta_diff_utils_unittest.cc
+++ b/payload_generator/delta_diff_utils_unittest.cc
@@ -197,9 +197,9 @@
   // Make a blob with random data that won't compress well.
   brillo::Blob random_data;
   std::mt19937 gen(12345);
-  std::uniform_int_distribution<uint8_t> dis(0, 255);
+  std::uniform_int_distribution<uint16_t> dis(0, 255);
   for (uint32_t i = 0; i < kBlockSize; i++) {
-    random_data.push_back(dis(gen));
+    random_data.push_back(static_cast<uint8_t>(dis(gen)));
   }
 
   for (int i = 0; i < 2; i++) {