diff --git a/scripts/generate_oxr_ext_support.py b/scripts/generate_oxr_ext_support.py
index 752fea21e..f60a58d96 100755
--- a/scripts/generate_oxr_ext_support.py
+++ b/scripts/generate_oxr_ext_support.py
@@ -40,7 +40,7 @@ EXTENSIONS = (
     ['XR_KHR_composition_layer_depth', 'XRT_FEATURE_OPENXR_LAYER_DEPTH'],
     ['XR_KHR_composition_layer_equirect', 'XRT_FEATURE_OPENXR_LAYER_EQUIRECT1'],
     ['XR_KHR_composition_layer_equirect2', 'XRT_FEATURE_OPENXR_LAYER_EQUIRECT2'],
-    ['XR_KHR_convert_timespec_time', 'XR_USE_TIMESPEC'],
+    ['XR_KHR_convert_timespec_time', 'XR_USE_TIMESPEC', not_('XR_USE_PLATFORM_WIN32')],
     ['XR_KHR_D3D11_enable', 'XR_USE_GRAPHICS_API_D3D11'],
     ['XR_KHR_D3D12_enable', 'XR_USE_GRAPHICS_API_D3D12'],
     ['XR_KHR_loader_init', 'XR_USE_PLATFORM_ANDROID'],
diff --git a/src/xrt/state_trackers/oxr/oxr_api_instance.c b/src/xrt/state_trackers/oxr/oxr_api_instance.c
index e0417ec2c..97f5bb84e 100644
--- a/src/xrt/state_trackers/oxr/oxr_api_instance.c
+++ b/src/xrt/state_trackers/oxr/oxr_api_instance.c
@@ -355,7 +355,7 @@ oxr_xrPathToString(
 }
 
 // ---- XR_KHR_convert_timespec_time extension
-#ifdef XR_USE_TIMESPEC
+#ifdef OXR_HAVE_KHR_convert_timespec_time
 XrResult
 oxr_xrConvertTimespecTimeToTimeKHR(XrInstance instance, const struct timespec *timespecTime, XrTime *time)
 {
@@ -390,7 +390,7 @@ oxr_xrConvertTimeToTimespecTimeKHR(XrInstance instance, XrTime time, struct time
 	return oxr_instance_convert_time_to_timespec(&log, inst, time, timespecTime);
 }
 
-#endif // XR_USE_TIMESPEC
+#endif // OXR_HAVE_KHR_convert_timespec_time
 
 // ---- XR_KHR_win32_convert_performance_counter_time extension
 #ifdef XR_USE_PLATFORM_WIN32
diff --git a/src/xrt/state_trackers/oxr/oxr_extension_support.h b/src/xrt/state_trackers/oxr/oxr_extension_support.h
index e0de0007a..1790d08a6 100644
--- a/src/xrt/state_trackers/oxr/oxr_extension_support.h
+++ b/src/xrt/state_trackers/oxr/oxr_extension_support.h
@@ -104,7 +104,7 @@
 /*
  * XR_KHR_convert_timespec_time
  */
-#if defined(XR_KHR_convert_timespec_time) && defined(XR_USE_TIMESPEC)
+#if defined(XR_KHR_convert_timespec_time) && defined(XR_USE_TIMESPEC) && (!defined(XR_USE_PLATFORM_WIN32))
 #define OXR_HAVE_KHR_convert_timespec_time
 #define OXR_EXTENSION_SUPPORT_KHR_convert_timespec_time(_) _(KHR_convert_timespec_time, KHR_CONVERT_TIMESPEC_TIME)
 #else