diff --git a/doc/changes/state_trackers/issue.63.md b/doc/changes/state_trackers/issue.63.md
new file mode 100644
index 000000000..f34aacd85
--- /dev/null
+++ b/doc/changes/state_trackers/issue.63.md
@@ -0,0 +1,6 @@
+---
+- issue.63
+- mr.256
+---
+
+Fix compilation issue in `st/gui` when building without OpenCV.
diff --git a/src/xrt/state_trackers/gui/gui_scene_calibrate.c b/src/xrt/state_trackers/gui/gui_scene_calibrate.c
index 57fd977a9..8d4b116db 100644
--- a/src/xrt/state_trackers/gui/gui_scene_calibrate.c
+++ b/src/xrt/state_trackers/gui/gui_scene_calibrate.c
@@ -57,6 +57,7 @@ struct calibration_scene
  *
  */
 
+#ifdef XRT_HAVE_OPENCV
 static void
 save_calibration(struct calibration_scene *cs)
 {
@@ -70,6 +71,7 @@ save_calibration(struct calibration_scene *cs)
 	// Free data, no longer needed.
 	t_stereo_camera_calibration_reference(&cs->status.stereo_data, NULL);
 }
+#endif
 
 static void
 draw_texture(struct gui_ogl_texture *tex, bool header)