diff --git a/cpdfcommand.ml b/cpdfcommand.ml
index 4024b99..64af924 100644
--- a/cpdfcommand.ml
+++ b/cpdfcommand.ml
@@ -1893,9 +1893,7 @@ let closepath () =
   addop Cpdfdraw.ClosePath
 
 let setthickness s =
-  try
-    addop (Cpdfdraw.SetLineThickness (float_of_string s))
-  with
+  try addop (Cpdfdraw.SetLineThickness (float_of_string s)) with
     _ -> error "Thickness must be a number"
 
 let setcap s =
@@ -1919,9 +1917,7 @@ let setjoin s =
     addop (Cpdfdraw.SetLineJoin num)
 
 let setmiter s = 
-  try
-    addop (Cpdfdraw.SetMiterLimit (float_of_string s))
-  with
+  try addop (Cpdfdraw.SetMiterLimit (float_of_string s)) with
     _ -> error "Miter limit must be a number"
 
 let setdash s =
@@ -2089,7 +2085,6 @@ let addspecialtext s =
 let addleading f =
   addop (Cpdfdraw.Leading f)
 
-
 let addcharspace f =
   addop (Cpdfdraw.CharSpace f)
 
diff --git a/cpdfdraw.ml b/cpdfdraw.ml
index 9ceee21..d39cc87 100644
--- a/cpdfdraw.ml
+++ b/cpdfdraw.ml
@@ -1,4 +1,5 @@
 open Pdfutil
+open Cpdferror
 
 type colspec =
    NoCol
@@ -93,7 +94,7 @@ let resstack =
   ref [empty_res ()]
 
 let res () =
-  hd !resstack
+  try hd !resstack with _ -> error "graphics stack empty"
 
 let rescopy r =
   {r with
@@ -106,7 +107,7 @@ let respush () =
   resstack := (rescopy (res ()))::!resstack
 
 let respop () =
-  let n = (hd !resstack).num in
+  let n = (res ()).num in
     resstack := tl !resstack;
     (* not necessary, since names are isolated in the xobject, but it makes
        manual debugging of PDF files easier if we don't re-use numbers *)
@@ -202,11 +203,11 @@ let rec ops_of_drawop pdf endpage filename bates batespad num page = function
       create_form_xobject a b c d pdf endpage filename bates batespad num page n ops;
       []
   | Use n ->
-      let pdfname = try fst (Hashtbl.find (res ()).form_xobjects n) with _ -> Cpdferror.error ("Form XObject not found: " ^ n) in
+      let pdfname = try fst (Hashtbl.find (res ()).form_xobjects n) with _ -> error ("Form XObject not found: " ^ n) in
         (res ()).page_names <- pdfname::(res ()).page_names;
         [Pdfops.Op_Do pdfname]
   | Image s ->
-      let pdfname = try fst (Hashtbl.find (res ()).images s) with _ -> Cpdferror.error ("Image not found: " ^ s) in
+      let pdfname = try fst (Hashtbl.find (res ()).images s) with _ -> error ("Image not found: " ^ s) in
         (res ()).page_names <- pdfname::(res ()).page_names;
         [Pdfops.Op_Do pdfname]
   | ImageXObject (s, obj) ->