diff --git a/test/blackbox/common/DDSBlackboxTestsDSAutoMode.cpp b/test/blackbox/common/DDSBlackboxTestsDSAutoMode.cpp
index 40358c156c..ef0bbb4611 100644
--- a/test/blackbox/common/DDSBlackboxTestsDSAutoMode.cpp
+++ b/test/blackbox/common/DDSBlackboxTestsDSAutoMode.cpp
@@ -185,7 +185,7 @@ TEST(DSAutoMode, ros_discovery_server_auto_env_correct_transports_are_used)
  */
 TEST(DSAutoMode, ros_discovery_server_auto_env_discovery_info)
 {
-    std::size_t num_writers = 3;
+    unsigned int num_writers = 3;
     std::vector<std::shared_ptr<PubSubWriter<HelloWorldPubSubType>>> writers;
     writers.reserve(num_writers);
     PubSubReader<HelloWorldPubSubType> reader_auto(TEST_TOPIC_NAME + "_auto");
@@ -254,7 +254,7 @@ TEST(DSAutoMode, ros_discovery_server_auto_env_discovery_info)
  */
 TEST(DSAutoMode, ros_discovery_server_auto_env_multiple_clients_multiple_domains)
 {
-    std::size_t num_writer_reader_pairs = 5;
+    unsigned int num_writer_reader_pairs = 5;
 
     std::vector<std::shared_ptr<PubSubWriter<HelloWorldPubSubType>>> writers;
     std::vector<std::shared_ptr<PubSubReader<HelloWorldPubSubType>>> readers;