diff --git a/rclcpp/src/rclcpp/node.cpp b/rclcpp/src/rclcpp/node.cpp
index ba63ce6279..7cc352b019 100644
--- a/rclcpp/src/rclcpp/node.cpp
+++ b/rclcpp/src/rclcpp/node.cpp
@@ -54,6 +54,12 @@ extend_sub_namespace(const std::string & existing_sub_namespace, const std::stri
             extension.c_str(),
             "a sub-namespace should not have a leading /",
             0);
+  } else if (existing_sub_namespace.empty() && extension.empty()) {
+    throw rclcpp::exceptions::NameValidationError(
+            "sub_namespace",
+            extension.c_str(),
+            "sub-nodes should not extend nodes by an empty sub-namespace",
+            0);
   }
 
   std::string new_sub_namespace;
@@ -79,7 +85,11 @@ create_effective_namespace(const std::string & node_namespace, const std::string
   // and do not need trimming of `/` and other things, as they were validated
   // in other functions already.
 
-  if (node_namespace.back() == '/') {
+  // A node may not have a sub_namespace if it is no sub_node. In this case,
+  // just return the original namespace
+  if (sub_namespace.empty()) {
+    return node_namespace;
+  } else if (node_namespace.back() == '/') {
     // this is the special case where node_namespace is just `/`
     return node_namespace + sub_namespace;
   } else {
diff --git a/rclcpp/test/rclcpp/test_node.cpp b/rclcpp/test/rclcpp/test_node.cpp
index 2c52b5264d..ae8b7e23f4 100644
--- a/rclcpp/test/rclcpp/test_node.cpp
+++ b/rclcpp/test/rclcpp/test_node.cpp
@@ -94,6 +94,7 @@ TEST_F(TestNode, get_name_and_namespace) {
     auto node = std::make_shared<rclcpp::Node>("my_node", "/ns");
     EXPECT_STREQ("my_node", node->get_name());
     EXPECT_STREQ("/ns", node->get_namespace());
+    EXPECT_STREQ("/ns", node->get_effective_namespace().c_str());
     EXPECT_STREQ("/ns/my_node", node->get_fully_qualified_name());
   }
   {
@@ -108,30 +109,35 @@ TEST_F(TestNode, get_name_and_namespace) {
     auto node = std::make_shared<rclcpp::Node>("my_node", "ns");
     EXPECT_STREQ("my_node", node->get_name());
     EXPECT_STREQ("/ns", node->get_namespace());
+    EXPECT_STREQ("/ns", node->get_effective_namespace().c_str());
     EXPECT_STREQ("/ns/my_node", node->get_fully_qualified_name());
   }
   {
     auto node = std::make_shared<rclcpp::Node>("my_node");
     EXPECT_STREQ("my_node", node->get_name());
     EXPECT_STREQ("/", node->get_namespace());
+    EXPECT_STREQ("/", node->get_effective_namespace().c_str());
     EXPECT_STREQ("/my_node", node->get_fully_qualified_name());
   }
   {
     auto node = std::make_shared<rclcpp::Node>("my_node", "");
     EXPECT_STREQ("my_node", node->get_name());
     EXPECT_STREQ("/", node->get_namespace());
+    EXPECT_STREQ("/", node->get_effective_namespace().c_str());
     EXPECT_STREQ("/my_node", node->get_fully_qualified_name());
   }
   {
     auto node = std::make_shared<rclcpp::Node>("my_node", "/my/ns");
     EXPECT_STREQ("my_node", node->get_name());
     EXPECT_STREQ("/my/ns", node->get_namespace());
+    EXPECT_STREQ("/my/ns", node->get_effective_namespace().c_str());
     EXPECT_STREQ("/my/ns/my_node", node->get_fully_qualified_name());
   }
   {
     auto node = std::make_shared<rclcpp::Node>("my_node", "my/ns");
     EXPECT_STREQ("my_node", node->get_name());
     EXPECT_STREQ("/my/ns", node->get_namespace());
+    EXPECT_STREQ("/my/ns", node->get_effective_namespace().c_str());
     EXPECT_STREQ("/my/ns/my_node", node->get_fully_qualified_name());
   }
   {
@@ -270,6 +276,13 @@ TEST_F(TestNode, subnode_construction_and_destruction) {
       auto subnode = node->create_sub_node("~sub_ns");
     }, rclcpp::exceptions::InvalidNamespaceError);
   }
+  {
+    ASSERT_THROW(
+    {
+      auto node = std::make_shared<rclcpp::Node>("my_node", "/ns");
+      auto subnode = node->create_sub_node("");
+    }, rclcpp::exceptions::NameValidationError);
+  }
 }
 
 TEST_F(TestNode, get_logger) {