diff --git a/rmw/include/rmw/validate_node_name.h b/rmw/include/rmw/validate_node_name.h
index 609ebefc..39d045ca 100644
--- a/rmw/include/rmw/validate_node_name.h
+++ b/rmw/include/rmw/validate_node_name.h
@@ -82,7 +82,7 @@ rmw_validate_node_name(
   int * validation_result,
   size_t * invalid_index);
 
-/// Return a string to describe the validation result, or NULL if unknown.
+/// Return a validation result description, or NULL if unknown or RMW_NODE_NAME_VALID.
 RMW_PUBLIC
 RMW_WARN_UNUSED
 const char *
diff --git a/rmw/include/rmw/validate_topic_name.h b/rmw/include/rmw/validate_topic_name.h
index f36d5075..c953a3c6 100644
--- a/rmw/include/rmw/validate_topic_name.h
+++ b/rmw/include/rmw/validate_topic_name.h
@@ -88,7 +88,7 @@ rmw_validate_topic_name(
   int * validation_result,
   size_t * invalid_index);
 
-/// Return a string to describe the validation result, or NULL if unknown.
+/// Return a validation result description, or NULL if unknown or RMW_TOPIC_VALID.
 RMW_PUBLIC
 RMW_WARN_UNUSED
 const char *
diff --git a/rmw/src/validate_node_name.c b/rmw/src/validate_node_name.c
index 4f5f2805..b15a5a38 100644
--- a/rmw/src/validate_node_name.c
+++ b/rmw/src/validate_node_name.c
@@ -77,7 +77,7 @@ rmw_node_name_validation_result_string(int validation_result)
 {
   switch (validation_result) {
     case RMW_NODE_NAME_VALID:
-      return "node name is valid";
+      return NULL;
     case RMW_NODE_NAME_INVALID_IS_EMPTY_STRING:
       return "node name must not be empty";
     case RMW_NODE_NAME_INVALID_CONTAINS_UNALLOWED_CHARACTERS:
diff --git a/rmw/src/validate_topic_name.c b/rmw/src/validate_topic_name.c
index dec57b66..69ff18ed 100644
--- a/rmw/src/validate_topic_name.c
+++ b/rmw/src/validate_topic_name.c
@@ -107,7 +107,7 @@ rmw_topic_validation_result_string(int validation_result)
 {
   switch (validation_result) {
     case RMW_TOPIC_VALID:
-      return "topic name is valid";
+      return NULL;
     case RMW_TOPIC_INVALID_IS_EMPTY_STRING:
       return "topic name must not be empty";
     case RMW_TOPIC_INVALID_NOT_ABSOLUTE:
diff --git a/rmw/test/test_validate_node_name.cpp b/rmw/test/test_validate_node_name.cpp
index 40a16a12..f14f841c 100644
--- a/rmw/test/test_validate_node_name.cpp
+++ b/rmw/test/test_validate_node_name.cpp
@@ -43,7 +43,7 @@ TEST(test_validate_node_name, valid_node_name) {
   ASSERT_EQ(RMW_RET_OK, ret);
   ASSERT_EQ(RMW_NODE_NAME_VALID, validation_result);
 
-  ASSERT_NE((char *)NULL, rmw_node_name_validation_result_string(validation_result));
+  ASSERT_EQ((char *)NULL, rmw_node_name_validation_result_string(validation_result));
 }
 
 TEST(test_validate_node_name, empty_node_name) {
diff --git a/rmw/test/test_validate_topic_name.cpp b/rmw/test/test_validate_topic_name.cpp
index 8eaee6ba..0704b87f 100644
--- a/rmw/test/test_validate_topic_name.cpp
+++ b/rmw/test/test_validate_topic_name.cpp
@@ -43,7 +43,7 @@ TEST(test_validate_topic_name, valid_topic) {
   ASSERT_EQ(RMW_RET_OK, ret);
   ASSERT_EQ(RMW_TOPIC_VALID, validation_result);
 
-  ASSERT_NE((char *)NULL, rmw_topic_validation_result_string(validation_result));
+  ASSERT_EQ((char *)NULL, rmw_topic_validation_result_string(validation_result));
 }
 
 TEST(test_validate_topic_name, empty_topic_name) {