diff --git a/rmw_fastrtps_shared_cpp/src/namespace_prefix.cpp b/rmw_fastrtps_shared_cpp/src/namespace_prefix.cpp
index 4945e8518..d02fd0d51 100644
--- a/rmw_fastrtps_shared_cpp/src/namespace_prefix.cpp
+++ b/rmw_fastrtps_shared_cpp/src/namespace_prefix.cpp
@@ -31,10 +31,8 @@ const std::vector<std::string> _ros_prefixes =
 std::string
 _resolve_prefix(const std::string & name, const std::string & prefix)
 {
-  if (name.length() > prefix.length()) {
-    if (name.rfind(prefix, 0) == 0 && name.at(prefix.length()) == '/') {
-      return name.substr(prefix.length());
-    }
+  if (name.rfind(prefix + "/", 0) == 0) {
+    return name.substr(prefix.length());
   }
   return "";
 }
@@ -44,10 +42,8 @@ std::string
 _get_ros_prefix_if_exists(const std::string & topic_name)
 {
   for (const auto & prefix : _ros_prefixes) {
-    if (topic_name.length() > prefix.length()) {
-      if (topic_name.rfind(prefix, 0) == 0 && topic_name.at(prefix.length()) == '/') {
-        return prefix;
-      }
+    if (topic_name.rfind(prefix + "/", 0) == 0) {
+      return prefix;
     }
   }
   return "";
@@ -58,10 +54,8 @@ std::string
 _strip_ros_prefix_if_exists(const std::string & topic_name)
 {
   for (const auto & prefix : _ros_prefixes) {
-    if (topic_name.length() > prefix.length()) {
-      if (topic_name.rfind(prefix, 0) == 0 && topic_name.at(prefix.length()) == '/') {
-        return topic_name.substr(prefix.length());
-      }
+    if (topic_name.rfind(prefix + "/", 0) == 0) {
+      return topic_name.substr(prefix.length());
     }
   }
   return topic_name;