diff --git a/hw/qxl.c b/hw/qxl.c
index 28c8b5d0d9..c50eaf9ac1 100644
--- a/hw/qxl.c
+++ b/hw/qxl.c
@@ -125,13 +125,18 @@ static void qxl_reset_memslots(PCIQXLDevice *d);
 static void qxl_reset_surfaces(PCIQXLDevice *d);
 static void qxl_ring_set_dirty(PCIQXLDevice *qxl);
 
-void qxl_guest_bug(PCIQXLDevice *qxl, const char *msg)
+void qxl_guest_bug(PCIQXLDevice *qxl, const char *msg, ...)
 {
 #if SPICE_INTERFACE_QXL_MINOR >= 1
     qxl_send_events(qxl, QXL_INTERRUPT_ERROR);
 #endif
     if (qxl->guestdebug) {
-        fprintf(stderr, "qxl-%d: guest bug: %s\n", qxl->id, msg);
+        va_list ap;
+        va_start(ap, msg);
+        fprintf(stderr, "qxl-%d: guest bug: ", qxl->id);
+        vfprintf(stderr, msg, ap);
+        fprintf(stderr, "\n");
+        va_end(ap);
     }
 }
 
diff --git a/hw/qxl.h b/hw/qxl.h
index 5db9aaee2f..32ca5a0895 100644
--- a/hw/qxl.h
+++ b/hw/qxl.h
@@ -99,7 +99,7 @@ typedef struct PCIQXLDevice {
 
 /* qxl.c */
 void *qxl_phys2virt(PCIQXLDevice *qxl, QXLPHYSICAL phys, int group_id);
-void qxl_guest_bug(PCIQXLDevice *qxl, const char *msg);
+void qxl_guest_bug(PCIQXLDevice *qxl, const char *msg, ...);
 
 void qxl_spice_update_area(PCIQXLDevice *qxl, uint32_t surface_id,
                            struct QXLRect *area, struct QXLRect *dirty_rects,