diff --git a/renderdoc/driver/vulkan/vk_core.cpp b/renderdoc/driver/vulkan/vk_core.cpp
index 3726e36e6..1633b5f95 100644
--- a/renderdoc/driver/vulkan/vk_core.cpp
+++ b/renderdoc/driver/vulkan/vk_core.cpp
@@ -644,6 +644,9 @@ static VkResult FillPropertyCountAndList(const VkExtensionProperties *src, uint3
   {
     uint32_t dstSpace = *dstCount;
 
+    // return the number of extensions.
+    *dstCount = numExts;
+
     // copy as much as there's space for, up to how many there are
     memcpy(dstProps, src, sizeof(VkExtensionProperties) * RDCMIN(numExts, dstSpace));