diff --git a/renderdoc/driver/vulkan/vk_layer.cpp b/renderdoc/driver/vulkan/vk_layer.cpp
index 2b13c0b24..515f272bd 100644
--- a/renderdoc/driver/vulkan/vk_layer.cpp
+++ b/renderdoc/driver/vulkan/vk_layer.cpp
@@ -437,9 +437,8 @@ VK_LAYER_RENDERDOC_CaptureGetDeviceProcAddr(VkDevice device, const char *pName)
     HookInitVulkanInstanceExts();
   }
 
-  if(GetDeviceDispatchTable(device)->GetDeviceProcAddr == NULL)
-    return NULL;
-  return GetDeviceDispatchTable(device)->GetDeviceProcAddr(Unwrap(device), pName);
+  // unknown or not-enabled functions must return NULL
+  return NULL;
 }
 
 VK_LAYER_EXPORT VKAPI_ATTR PFN_vkVoidFunction VKAPI_CALL
@@ -448,6 +447,12 @@ VK_LAYER_RENDERDOC_Capture_layerGetPhysicalDeviceProcAddr(VkInstance instance, c
 VK_LAYER_EXPORT VKAPI_ATTR PFN_vkVoidFunction VKAPI_CALL
 VK_LAYER_RENDERDOC_CaptureGetInstanceProcAddr(VkInstance instance, const char *pName)
 {
+  // if name is NULL undefined is returned, let's return NULL
+  if(pName == NULL)
+    return NULL;
+
+  // a NULL instance can return vkGetInstanceProcAddr or a global function, handle that here
+
   if(!strcmp("vkGetInstanceProcAddr", pName))
     return (PFN_vkVoidFunction)&VK_LAYER_RENDERDOC_CaptureGetInstanceProcAddr;
   if(!strcmp("vkEnumerateInstanceExtensionProperties", pName))
@@ -455,6 +460,9 @@ VK_LAYER_RENDERDOC_CaptureGetInstanceProcAddr(VkInstance instance, const char *p
   if(!strcmp("vk_layerGetPhysicalDeviceProcAddr", pName))
     return (PFN_vkVoidFunction)&VK_LAYER_RENDERDOC_Capture_layerGetPhysicalDeviceProcAddr;
 
+  // don't implement vkEnumerateInstanceLayerProperties or vkEnumerateInstanceVersion, the loader
+  // will do that
+
   HookInit(CreateInstance);
 
   if(instance == VK_NULL_HANDLE)
@@ -471,6 +479,9 @@ VK_LAYER_RENDERDOC_CaptureGetInstanceProcAddr(VkInstance instance, const char *p
   if(!strcmp("vkDestroyDevice", pName))
     return (PFN_vkVoidFunction)&hooked_vkDestroyDevice;
 
+  // we should only return a function pointer for functions that are either from a supported core
+  // version, an enabled instance extension or an _available_ device extension
+
   HookInitVulkanInstance();
 
   InstanceDeviceInfo *instDevInfo = NULL;
@@ -509,16 +520,17 @@ VK_LAYER_RENDERDOC_CaptureGetInstanceProcAddr(VkInstance instance, const char *p
 
   HookInitVulkanInstanceExts_PhysDev();
 
-  if(GetInstanceDispatchTable(instance)->GetInstanceProcAddr == NULL)
-    return NULL;
-  return GetInstanceDispatchTable(instance)->GetInstanceProcAddr(Unwrap(instance), pName);
+  // all other functions must return NULL so that GIPA can be used with NULL checks sensibly for
+  // missing functionality
+
+  return NULL;
 }
 
 VK_LAYER_EXPORT VKAPI_ATTR PFN_vkVoidFunction VKAPI_CALL
 VK_LAYER_RENDERDOC_Capture_layerGetPhysicalDeviceProcAddr(VkInstance instance, const char *pName)
 {
   // GetPhysicalDeviceProcAddr acts like GetInstanceProcAddr but it returns NULL for any functions
-  // which aren't physical device functions
+  // which are known but aren't physical device functions
   if(!strcmp("vkGetInstanceProcAddr", pName))
     return NULL;
   if(!strcmp("vk_layerGetPhysicalDeviceProcAddr", pName))
@@ -589,14 +601,14 @@ VK_LAYER_RENDERDOC_Capture_layerGetPhysicalDeviceProcAddr(VkInstance instance, c
   if(GetInstanceDispatchTable(instance)->GetInstanceProcAddr == NULL)
     return NULL;
 
-  PFN_vkGetInstanceProcAddr GPDA =
+  PFN_vkGetInstanceProcAddr GPDPA =
       (PFN_vkGetInstanceProcAddr)GetInstanceDispatchTable(instance)->GetInstanceProcAddr(
           Unwrap(instance), "vk_layerGetPhysicalDeviceProcAddr");
 
-  if(GPDA == NULL)
+  if(GPDPA == NULL)
     return NULL;
 
-  return GPDA(Unwrap(instance), pName);
+  return GPDPA(Unwrap(instance), pName);
 }
 
 // layer interface negotation (new interface)