diff --git a/base b/base
index cbb585960..2d733e38d 160000
--- a/base
+++ b/base
@@ -1 +1 @@
-Subproject commit cbb585960ab33f8a3d22e52c48bc79dee57b7cf7
+Subproject commit 2d733e38de74b54dd6ace933a94cbc09b40fdd4d
diff --git a/frontend/document/pdfdocument.lua b/frontend/document/pdfdocument.lua
index 0b4c82011..706f2a706 100644
--- a/frontend/document/pdfdocument.lua
+++ b/frontend/document/pdfdocument.lua
@@ -119,6 +119,9 @@ end
 
 function PdfDocument:saveHighlight(pageno, item)
     self.is_edited = true
+    local ffi = require("ffi")
+    -- will also need mupdf_h.lua to be evaluated once
+    -- but this is guaranteed at this point
     local n = #item.pboxes
     local quadpoints = ffi.new("fz_point[?]", 4*n)
     for i=1, n do