diff --git a/exa/exa_migration.c b/exa/exa_migration.c
index 57d651f80..06a4b9330 100644
--- a/exa/exa_migration.c
+++ b/exa/exa_migration.c
@@ -435,6 +435,8 @@ exaAssertNotDirty (PixmapPtr pPixmap)
 	if (memcmp(dst, src, data_row_bytes) != 0) {
 	     abort();
 	}
+	dst += dst_pitch;
+	src += src_pitch;
     }
     exaFinishAccess(&pPixmap->drawable, EXA_PREPARE_SRC);
 }