diff --git a/libweston/backend-drm/drm.c b/libweston/backend-drm/drm.c
index 8f58e4618..17013edfb 100644
--- a/libweston/backend-drm/drm.c
+++ b/libweston/backend-drm/drm.c
@@ -1215,16 +1215,17 @@ drm_repaint_flush(struct weston_backend *backend)
 {
 	struct drm_backend *b = container_of(backend, struct drm_backend, base);
 	struct drm_device *device;
+	FILE *dbg;
 
 	WESTON_TRACE_FUNC();
 
 	wl_list_for_each(device, &b->kms_list, link)
 		drm_repaint_flush_device(device);
 
-	if (weston_log_scope_is_enabled(b->debug)) {
-		char *dbg = weston_compositor_print_scene_graph(b->compositor);
-		drm_debug(b, "%s", dbg);
-		free(dbg);
+	dbg = weston_log_scope_stream(b->debug);
+	if (dbg) {
+		weston_compositor_print_scene_graph(b->compositor, dbg);
+		fflush(dbg);
 	}
 }
 
diff --git a/libweston/compositor.c b/libweston/compositor.c
index 2f198f03c..8a4d84054 100644
--- a/libweston/compositor.c
+++ b/libweston/compositor.c
@@ -9759,25 +9759,25 @@ debug_scene_view_print_tree(struct weston_view *view, FILE *fp)
  * Output information on how libweston is currently composing the scene
  * graph.
  *
+ * \param ec The compositor has a single scene-graph.
+ * \param fp A writable stream where the scene-graph is printed.
+ * Can also be NULL to skip printing.
+ *
  * \ingroup compositor
  */
-WL_EXPORT char *
-weston_compositor_print_scene_graph(struct weston_compositor *ec)
+WL_EXPORT void
+weston_compositor_print_scene_graph(struct weston_compositor *ec, FILE *fp)
 {
 	struct weston_output *output;
 	struct weston_layer *layer;
 	struct timespec now;
 	int layer_idx = 0;
-	FILE *fp;
-	char *ret;
-	size_t len;
-	int err;
+
+	if (!fp)
+		return;
 
 	WESTON_TRACE_FUNC();
 
-	fp = open_memstream(&ret, &len);
-	assert(fp);
-
 	weston_compositor_read_presentation_clock(ec, &now);
 	fprintf(fp, "Weston scene graph at %" PRId64 ".%09ld:\n\n",
 		(int64_t)now.tv_sec, now.tv_nsec);
@@ -9849,11 +9849,6 @@ weston_compositor_print_scene_graph(struct weston_compositor *ec)
 
 		fprintf(fp, "\n");
 	}
-
-	err = fclose(fp);
-	assert(err == 0);
-
-	return ret;
 }
 
 static void
@@ -9891,6 +9886,7 @@ static void
 debug_scene_graph_cb(struct weston_log_subscription *sub, void *data)
 {
 	struct weston_compositor *ec = data;
+	FILE *fp;
 	char *str;
 
 	/* If the presentation_clock is CLOCK_REALTIME, then it is
@@ -9899,7 +9895,9 @@ debug_scene_graph_cb(struct weston_log_subscription *sub, void *data)
 	if (ec->presentation_clock == CLOCK_REALTIME)
 		return;
 
-	str = weston_compositor_print_scene_graph(ec);
+	fp = open_memstream(&str, NULL);
+	weston_compositor_print_scene_graph(ec, fp);
+	fclose(fp);
 
 	weston_log_subscription_write(sub, str, strlen(str));
 	free(str);
diff --git a/libweston/libweston-internal.h b/libweston/libweston-internal.h
index ebd1cbed9..7e0ebb049 100644
--- a/libweston/libweston-internal.h
+++ b/libweston/libweston-internal.h
@@ -329,8 +329,8 @@ weston_compositor_dmabuf_can_scanout(struct weston_compositor *compositor,
 void
 weston_compositor_offscreen(struct weston_compositor *compositor);
 
-char *
-weston_compositor_print_scene_graph(struct weston_compositor *ec);
+void
+weston_compositor_print_scene_graph(struct weston_compositor *ec, FILE *fp);
 
 void
 weston_compositor_read_presentation_clock(