diff --git a/test/modernish.t b/test/modernish.t
index 114e56e..961c95b 100644
--- a/test/modernish.t
+++ b/test/modernish.t
@@ -3,7 +3,7 @@ These these are from parts of the modernish checks.
   $ cat > arith.sh << EOF
   > i=7
   > j=0
-  > case \$(( ( (j+=6*i)==0x2A)>0 ? 014 : 015 )) in
+  > case \$(( ((j+=6*i)==0x2A)>0 ? 014 : 015 )) in
   >   ( 12 | 14 ) ;;	# OK or BUG_NOOCTAL
   >   ( * )	exit ;;
   > esac
diff --git a/vendor/morbig.0.11.0/src/prelexer.mll b/vendor/morbig.0.11.0/src/prelexer.mll
index 4e00453..b741a37 100644
--- a/vendor/morbig.0.11.0/src/prelexer.mll
+++ b/vendor/morbig.0.11.0/src/prelexer.mll
@@ -433,7 +433,7 @@ rule token current = parse
 | "$((" {
     debug ~rule:"arithmetic-exp" lexbuf current;
     let current = push_arith current in
-    let current = next_double_rparen 1 current lexbuf in
+    let current = next_double_rparen true 1 current lexbuf in
     token current lexbuf
   }
 
@@ -714,15 +714,15 @@ and close_subshell expected_closing_char current = parse
      lexing_error lexbuf (Printf.sprintf "Unclosed subshell (got '%c')" c)
   }
 
-and next_double_rparen dplevel current = parse
+and next_double_rparen in_arith dplevel current = parse
   | "((" {
     let current = push_string current "((" in
-    next_double_rparen (dplevel+1) current lexbuf
+    next_double_rparen in_arith (if in_arith then dplevel else dplevel+1) current lexbuf
   }
-| "$((" {
+  | "$((" {
     debug ~rule:"arithmetic-exp" lexbuf current;
     let current = push_arith current in
-    let current = next_double_rparen (dplevel+1) current lexbuf in
+    let current = next_double_rparen true (dplevel+1) current lexbuf in
     current
   }
   | '`' as op | "$" ( '(' as op) {
@@ -731,20 +731,20 @@ and next_double_rparen dplevel current = parse
     let current = subshell op escaping_level current lexbuf in
     let expected_closing_char = if op = '`' then '`' else ')' in
     let current = close_subshell expected_closing_char current lexbuf in
-    next_double_rparen dplevel current lexbuf
+    next_double_rparen in_arith dplevel current lexbuf
   }
   | "))" {
     let current = pop_arith current in
     if dplevel = 1
     then current
-    else if dplevel > 1 then next_double_rparen (dplevel-1) current lexbuf
+    else if dplevel > 1 then next_double_rparen false (dplevel-1) current lexbuf
     else assert false
   }
   | eof {
     lexing_error lexbuf "Unterminated arithmetic expression."
   }
   | _ as c {
-    next_double_rparen dplevel (push_character current c) lexbuf
+    next_double_rparen in_arith dplevel (push_character current c) lexbuf
   }
 
 (*specification: