diff --git a/src/xrt/include/xrt/xrt_vulkan_includes.h b/src/xrt/include/xrt/xrt_vulkan_includes.h
index deb086bda..dee4caa92 100644
--- a/src/xrt/include/xrt/xrt_vulkan_includes.h
+++ b/src/xrt/include/xrt/xrt_vulkan_includes.h
@@ -11,3 +11,9 @@
 
 #define VK_NO_PROTOTYPES
 #include <vulkan/vulkan.h>
+
+#ifdef __cplusplus
+extern "C"
+#endif
+    VKAPI_ATTR PFN_vkVoidFunction VKAPI_CALL
+    vkGetInstanceProcAddr(VkInstance instance, const char *pName);
diff --git a/src/xrt/state_trackers/oxr/oxr_session_vk.c b/src/xrt/state_trackers/oxr/oxr_session_vk.c
index e405ee8dd..96740a1cb 100644
--- a/src/xrt/state_trackers/oxr/oxr_session_vk.c
+++ b/src/xrt/state_trackers/oxr/oxr_session_vk.c
@@ -19,10 +19,6 @@
 #include "oxr_two_call.h"
 #include "oxr_handle.h"
 
-
-VKAPI_ATTR PFN_vkVoidFunction VKAPI_CALL
-vkGetInstanceProcAddr(VkInstance instance, const char *pName);
-
 XrResult
 oxr_session_populate_vk(struct oxr_logger *log,
                         struct oxr_system *sys,