diff --git a/rclcpp_action/test/test_types.cpp b/rclcpp_action/test/test_types.cpp
index 8e7677d532..f981261105 100644
--- a/rclcpp_action/test/test_types.cpp
+++ b/rclcpp_action/test/test_types.cpp
@@ -12,7 +12,6 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-
 #include <gtest/gtest.h>
 
 #include <limits>
@@ -20,17 +19,17 @@
 
 TEST(TestActionTypes, goal_uuid_to_string) {
   rclcpp_action::GoalUUID goal_id;
-  for (size_t i = 0; i < UUID_SIZE; ++i) {
+  for (uint8_t i = 0; i < UUID_SIZE; ++i) {
     goal_id[i] = i;
   }
   EXPECT_STREQ("0123456789abcdef", rclcpp_action::to_string(goal_id).c_str());
 
-  for (size_t i = 0; i < UUID_SIZE; ++i) {
+  for (uint8_t i = 0; i < UUID_SIZE; ++i) {
     goal_id[i] = 16u + i;
   }
   EXPECT_STREQ("101112131415161718191a1b1c1d1e1f", rclcpp_action::to_string(goal_id).c_str());
 
-  for (size_t i = 0; i < UUID_SIZE; ++i) {
+  for (uint8_t i = 0; i < UUID_SIZE; ++i) {
     goal_id[i] = std::numeric_limits<uint8_t>::max() - i;
   }
   EXPECT_STREQ("fffefdfcfbfaf9f8f7f6f5f4f3f2f1f0", rclcpp_action::to_string(goal_id).c_str());
@@ -38,25 +37,25 @@ TEST(TestActionTypes, goal_uuid_to_string) {
 
 TEST(TestActionTypes, goal_uuid_to_rcl_action_goal_info) {
   rclcpp_action::GoalUUID goal_id;
-  for (size_t i = 0; i < UUID_SIZE; ++i) {
+  for (uint8_t i = 0; i < UUID_SIZE; ++i) {
     goal_id[i] = i;
   }
   rcl_action_goal_info_t goal_info = rcl_action_get_zero_initialized_goal_info();
   rclcpp_action::convert(goal_id, &goal_info);
-  for (size_t i = 0; i < UUID_SIZE; ++i) {
+  for (uint8_t i = 0; i < UUID_SIZE; ++i) {
     EXPECT_EQ(goal_info.goal_id.uuid[i], goal_id[i]);
   }
 }
 
 TEST(TestActionTypes, rcl_action_goal_info_to_goal_uuid) {
   rcl_action_goal_info_t goal_info = rcl_action_get_zero_initialized_goal_info();
-  for (size_t i = 0; i < UUID_SIZE; ++i) {
+  for (uint8_t i = 0; i < UUID_SIZE; ++i) {
     goal_info.goal_id.uuid[i] = i;
   }
 
   rclcpp_action::GoalUUID goal_id;
   rclcpp_action::convert(goal_id, &goal_info);
-  for (size_t i = 0; i < UUID_SIZE; ++i) {
+  for (uint8_t i = 0; i < UUID_SIZE; ++i) {
     EXPECT_EQ(goal_info.goal_id.uuid[i], goal_id[i]);
   }
 }