diff --git a/cpdfjpeg2000.ml b/cpdfjpeg2000.ml
index ac058ed..a2e98ed 100644
--- a/cpdfjpeg2000.ml
+++ b/cpdfjpeg2000.ml
@@ -35,6 +35,6 @@ let jpeg2000_dimensions_inner bs =
     done
 
 let jpeg2000_dimensions bs =
-  try jpeg2000_dimensions_inner bs; (0, 0) with
+  try ignore (jpeg2000_dimensions_inner bs); (0, 0) with
   | Answer (w, h) -> (w, h)
   | Exit -> error "could not determine JPEG2000 dimensions"