diff --git a/tools/hello.cpp b/tools/hello.cpp
index f280ac1..0ea1394 100644
--- a/tools/hello.cpp
+++ b/tools/hello.cpp
@@ -14,7 +14,6 @@
 
 
 ///////////////////////////////////////////////////////////////////////////////
-#if 0
 static VkBool32
 vk_debug_callback (VkDebugReportFlagsEXT flags,
                    VkDebugReportObjectTypeEXT objType,
@@ -38,7 +37,6 @@ vk_debug_callback (VkDebugReportFlagsEXT flags,
 
     return VK_FALSE;
 }
-#endif
 
 
 VkShaderModule
@@ -93,6 +91,20 @@ main (void)
         util::make_view (extensions.data (), extensions.data () + extensions.size ())
     );
 
+    {
+        VkDebugReportCallbackEXT callback;
+        VkDebugReportCallbackCreateInfoEXT debug_info {};
+        debug_info.sType = VK_STRUCTURE_TYPE_DEBUG_REPORT_CREATE_INFO_EXT;
+        debug_info.flags = VK_DEBUG_REPORT_ERROR_BIT_EXT | VK_DEBUG_REPORT_WARNING_BIT_EXT;
+        debug_info.pfnCallback = vk_debug_callback;
+
+        auto func = (decltype(&vkCreateDebugReportCallbackEXT))vkGetInstanceProcAddr (instance.id (),"vkCreateDebugReportCallbackEXT");
+
+        cruft::vk::error::try_code (
+            func (instance.id (), &debug_info, nullptr, &callback)
+        );
+    }
+
     auto pdevices = cruft::vk::physical_device::find (instance);
     auto &pdevice = pdevices[0];
 
@@ -438,7 +450,7 @@ main (void)
 
 
     std::vector<VkFramebuffer> swapchain_framebuffers (swap_image_views.size ());
-    for (int i = 0; i < swap_image_views.size (); ++i) {
+    for (size_t i = 0; i < swap_image_views.size (); ++i) {
         VkImageView attachments[] = {
             swap_image_views[i]
         };
@@ -476,7 +488,7 @@ main (void)
         vkAllocateCommandBuffers (ldevice.id (), &alloc_info, command_buffers.data ())
     );
 
-    for (int i = 0; i < command_buffers.size (); ++i) {
+    for (size_t i = 0; i < command_buffers.size (); ++i) {
         VkCommandBufferBeginInfo command_begin {};
         command_begin.sType = VK_STRUCTURE_TYPE_COMMAND_BUFFER_BEGIN_INFO;
         command_begin.flags = VK_COMMAND_BUFFER_USAGE_SIMULTANEOUS_USE_BIT;