diff --git a/src/Tiny_httpd_util.ml b/src/Tiny_httpd_util.ml
index 6dd12717..6aac8a02 100644
--- a/src/Tiny_httpd_util.ml
+++ b/src/Tiny_httpd_util.ml
@@ -3,31 +3,16 @@ let percent_encode ?(skip=fun _->false) s =
   String.iter
     (function
       | c when skip c -> Buffer.add_char buf c
-      | ' ' -> Buffer.add_string buf "%20"
-      | '!' -> Buffer.add_string buf "%21"
-      | '"' -> Buffer.add_string buf "%22"
-      | '#' -> Buffer.add_string buf "%23"
-      | '$' -> Buffer.add_string buf "%24"
-      | '%' -> Buffer.add_string buf "%25"
-      | '&' -> Buffer.add_string buf "%26"
-      | '\'' -> Buffer.add_string buf "%27"
-      | '(' -> Buffer.add_string buf "%28"
-      | ')' -> Buffer.add_string buf "%29"
-      | '*' -> Buffer.add_string buf "%2A"
-      | '+' -> Buffer.add_string buf "%2B"
-      | ',' -> Buffer.add_string buf "%2C"
-      | '/' -> Buffer.add_string buf "%2F"
-      | ':' -> Buffer.add_string buf "%3A"
-      | ';' -> Buffer.add_string buf "%3B"
-      | '=' -> Buffer.add_string buf "%3D"
-      | '?' -> Buffer.add_string buf "%3F"
-      | '@' -> Buffer.add_string buf "%40"
-      | '[' -> Buffer.add_string buf "%5B"
-      | ']' -> Buffer.add_string buf "%5D"
+      | (' ' | '!' | '"' | '#' | '$' | '%' | '&' | '\'' | '(' | ')' | '*' | '+'
+        | ',' | '/' | ':' | ';' | '=' | '?' | '@' | '[' | ']' | '~')
+        as c ->
+        Printf.bprintf buf "%%%x" (Char.code c)
       | c -> Buffer.add_char buf c)
     s;
   Buffer.contents buf
 
+let hex_int (s:string) : int = Scanf.sscanf s "%x" (fun x->x)
+
 let percent_decode (s:string) : _ option =
   let buf = Buffer.create (String.length s) in
   let i = ref 0 in
@@ -36,34 +21,15 @@ let percent_decode (s:string) : _ option =
       match String.get s !i with
       | '%' ->
         if !i+2 < String.length s then (
-          begin match String.sub s (!i+1) 2 with
-            | "20" -> Buffer.add_char buf ' '
-            | "21" -> Buffer.add_char buf '!'
-            | "22" -> Buffer.add_char buf '"'
-            | "23" -> Buffer.add_char buf '#'
-            | "24" -> Buffer.add_char buf '$'
-            | "25" -> Buffer.add_char buf '%'
-            | "26" -> Buffer.add_char buf '&'
-            | "27" -> Buffer.add_char buf '\''
-            | "28" -> Buffer.add_char buf '('
-            | "29" -> Buffer.add_char buf ')'
-            | "2A" -> Buffer.add_char buf '*'
-            | "2B" -> Buffer.add_char buf '+'
-            | "2C" -> Buffer.add_char buf ','
-            | "2F" -> Buffer.add_char buf '/'
-            | "3A" -> Buffer.add_char buf ':'
-            | "3B" -> Buffer.add_char buf ';'
-            | "3D" -> Buffer.add_char buf '='
-            | "3F" -> Buffer.add_char buf '?'
-            | "40" -> Buffer.add_char buf '@'
-            | "5B" -> Buffer.add_char buf '['
-            | "5D" -> Buffer.add_char buf ']'
-            | _ -> raise Exit
+          begin match hex_int @@ String.sub s (!i+1) 2 with
+            | n -> Buffer.add_char buf (Char.chr n)
+            | exception _ -> raise Exit
           end;
           i := !i + 3;
         ) else (
           raise Exit (* truncated *)
         )
+      | '+' -> Buffer.add_char buf ' '; incr i (* for query strings *)
       | c -> Buffer.add_char buf c; incr i
     done;
     Some (Buffer.contents buf)