diff --git a/sys/x86/x86/busdma_bounce.c b/sys/x86/x86/busdma_bounce.c
index 258441cf207..abbf64fd396 100644
--- a/sys/x86/x86/busdma_bounce.c
+++ b/sys/x86/x86/busdma_bounce.c
@@ -230,12 +230,13 @@ bounce_bus_dma_tag_set_domain(bus_dma_tag_t dmat)
 static int
 bounce_bus_dma_tag_destroy(bus_dma_tag_t dmat)
 {
-	bus_dma_tag_t dmat_copy __diagused;
+#ifdef KTR
+	bus_dma_tag_t dmat_copy = dmat;
+#endif
 	bus_dma_tag_t parent;
 	int error;
 
 	error = 0;
-	dmat_copy = dmat;
 
 	if (dmat != NULL) {
 		if (dmat->map_count != 0) {