diff --git a/src/sna/sna_accel.c b/src/sna/sna_accel.c
index 87d3217f..447d31a6 100644
--- a/src/sna/sna_accel.c
+++ b/src/sna/sna_accel.c
@@ -2445,6 +2445,7 @@ sna_pixmap_move_area_to_gpu(PixmapPtr pixmap, const BoxRec *box, unsigned int fl
 					pixmap->devPrivate.ptr = priv->ptr;
 					pixmap->devKind = priv->stride;
 				}
+				assert(!priv->mapped);
 				if (n == 1 && !priv->pinned &&
 				    box->x1 <= 0 && box->y1 <= 0 &&
 				    box->x2 >= pixmap->drawable.width &&
@@ -2489,6 +2490,7 @@ sna_pixmap_move_area_to_gpu(PixmapPtr pixmap, const BoxRec *box, unsigned int fl
 				pixmap->devPrivate.ptr = priv->ptr;
 				pixmap->devKind = priv->stride;
 			}
+			assert(!priv->mapped);
 			ok = sna_write_boxes(sna, pixmap,
 					     priv->gpu_bo, 0, 0,
 					     pixmap->devPrivate.ptr,
@@ -2524,6 +2526,7 @@ sna_pixmap_move_area_to_gpu(PixmapPtr pixmap, const BoxRec *box, unsigned int fl
 				pixmap->devPrivate.ptr = priv->ptr;
 				pixmap->devKind = priv->stride;
 			}
+			assert(!priv->mapped);
 			ok = sna_write_boxes(sna, pixmap,
 					     priv->gpu_bo, 0, 0,
 					     pixmap->devPrivate.ptr,
@@ -3108,6 +3111,7 @@ sna_pixmap_move_to_gpu(PixmapPtr pixmap, unsigned flags)
 				pixmap->devPrivate.ptr = priv->ptr;
 				pixmap->devKind = priv->stride;
 			}
+			assert(!priv->mapped);
 			if (n == 1 && !priv->pinned &&
 			    (box->x2 - box->x1) >= pixmap->drawable.width &&
 			    (box->y2 - box->y1) >= pixmap->drawable.height) {