diff --git a/dvipdfmx.def b/dvipdfmx.def
index a5cbf60..70e195d 100644
--- a/dvipdfmx.def
+++ b/dvipdfmx.def
@@ -93,14 +93,6 @@
          pdf:bgcolor \current@color}}
 \def\define@color@named#1#2{%
   \expandafter\let\csname col@#1\endcsname\@nnil}
-%
-% Graphics
-%
-\def\declareimagemask{%
-  \@ifnextchar[\declareimagemask@i{\declareimagemask@i[]}}
-\def\declareimagemask@i[#1]#2#3{%
-  \special{pdf:image @#2\space hide (#3) #1}}
-%
 % import from pdftex.def
 %
 \let\GPT@pagebox@option\@empty