diff --git a/CMakeLists.txt b/CMakeLists.txt
index b4c3cc9..6d8c16b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,7 +21,9 @@ SET(CMAKE_AUTOUIC ON)
 find_package(ament_cmake REQUIRED)
 find_package(rclcpp REQUIRED)
 find_package(Qt5 REQUIRED COMPONENTS Widgets)
-find_package(simulation_interfaces 1 REQUIRED)
+# Both the 1.x and 2.x message definitions are supported (see src/resource_compat.h).
+# The minimum version is 1.1.0, which introduced the world services.
+find_package(simulation_interfaces REQUIRED)
 find_package(rclcpp_action REQUIRED)
 find_package(tf2 REQUIRED)
 find_package(pluginlib REQUIRED)
diff --git a/README.md b/README.md
index 7d6cd4c..be05ab6 100644
--- a/README.md
+++ b/README.md
@@ -5,6 +5,8 @@ It utilizes https://github.com/ros-simulation/simulation_interfaces to change th
 
 # Prerequisites
 
+`simulation_interfaces` 1.1.0 or newer is required; both the 1.x and the 2.x message definitions are supported.
+
 ```shell
 sudo apt install ros-$ROS_DISTRO-simulation-interfaces libqt5-dev
 ```
diff --git a/src/resource_compat.h b/src/resource_compat.h
new file mode 100644
index 0000000..952258d
--- /dev/null
+++ b/src/resource_compat.h
@@ -0,0 +1,87 @@
+/* Copyright 2025, Robotec.ai sp. z o.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <type_traits>
+
+//! Compatibility helpers for the resource fields of simulation_interfaces.
+//!
+//! simulation_interfaces 2.0 replaced the flat `uri` and `resource_string` fields of
+//! SpawnEntity::Request, LoadWorld::Request and Spawnable with a single nested
+//! simulation_interfaces/msg/Resource member, named `entity_resource` or `world_resource`
+//! depending on the message. The accessors below resolve the field at compile time, so the
+//! panel builds against both the 1.x and the 2.x message definitions.
+
+namespace ResourceCompat
+{
+    template <typename T, typename = void>
+    struct HasEntityResource : std::false_type
+    {
+    };
+
+    template <typename T>
+    struct HasEntityResource<T, std::void_t<decltype(std::declval<T&>().entity_resource)>> : std::true_type
+    {
+    };
+
+    template <typename T, typename = void>
+    struct HasWorldResource : std::false_type
+    {
+    };
+
+    template <typename T>
+    struct HasWorldResource<T, std::void_t<decltype(std::declval<T&>().world_resource)>> : std::true_type
+    {
+    };
+} // namespace ResourceCompat
+
+//! Returns the `uri` field of a message, whether it is nested in a Resource member or not.
+//! Constness of the message is preserved in the returned reference.
+template <typename T>
+auto& ResourceUri(T& message)
+{
+    if constexpr (ResourceCompat::HasEntityResource<T>::value)
+    {
+        return message.entity_resource.uri;
+    }
+    else if constexpr (ResourceCompat::HasWorldResource<T>::value)
+    {
+        return message.world_resource.uri;
+    }
+    else
+    {
+        return message.uri;
+    }
+}
+
+//! Returns the `resource_string` field of a message, whether it is nested in a Resource member or not.
+//! Constness of the message is preserved in the returned reference.
+template <typename T>
+auto& ResourceString(T& message)
+{
+    if constexpr (ResourceCompat::HasEntityResource<T>::value)
+    {
+        return message.entity_resource.resource_string;
+    }
+    else if constexpr (ResourceCompat::HasWorldResource<T>::value)
+    {
+        return message.world_resource.resource_string;
+    }
+    else
+    {
+        return message.resource_string;
+    }
+}
diff --git a/src/simulation_widget.cpp b/src/simulation_widget.cpp
index 4d69041..bd5a3f7 100644
--- a/src/simulation_widget.cpp
+++ b/src/simulation_widget.cpp
@@ -22,6 +22,7 @@
 #include <simulation_interfaces/action/simulate_steps.hpp>
 #include <tf2/LinearMath/Quaternion.h>
 #include "quaternion_utils.h"
+#include "resource_compat.h"
 #include "service.h"
 #include "string_to_keys.h"
 #include "ui_sim_widget.h"
@@ -252,11 +253,11 @@ namespace q_simulation_interfaces
         auto selectedWorld = ui_->availableWorldsCombo->currentText();
         if (useUriForWorlds_)
         {
-            request.uri = selectedWorld.toStdString();
+            ResourceUri(request) = selectedWorld.toStdString();
         }
         else
         {
-            request.resource_string = selectedWorld.toStdString();
+            ResourceString(request) = selectedWorld.toStdString();
         }
 
         auto cb = [this](auto response)
@@ -729,7 +730,7 @@ namespace q_simulation_interfaces
 
         simulation_interfaces::srv::SpawnEntity::Request request;
         request.name = ui_->lineEditName->text().toStdString();
-        request.uri = ui_->ComboSpawables->currentText().toStdString();
+        ResourceUri(request) = ui_->ComboSpawables->currentText().toStdString();
         request.entity_namespace = ui_->lineEditNamespace->text().toStdString();
         request.allow_renaming = ui_->checkBoxAllowRename->isChecked();
         request.initial_pose.header.frame_id = ui_->spawnFrameLineEdit->text().toStdString();
@@ -780,11 +781,11 @@ namespace q_simulation_interfaces
 
                 auto spawnables = response->spawnables;
                 std::sort(spawnables.begin(), spawnables.end(),
-                          [](const auto& a, const auto& b) { return a.uri < b.uri; });
+                          [](const auto& a, const auto& b) { return ResourceUri(a) < ResourceUri(b); });
 
                 for (const auto& spawnable : spawnables)
                 {
-                    ui_->ComboSpawables->addItem(QString::fromStdString(spawnable.uri));
+                    ui_->ComboSpawables->addItem(QString::fromStdString(ResourceUri(spawnable)));
                 }
 
                 if (ui_->ComboSpawables->findText(selectedSpawnable) != -1)