diff --git a/README.md b/README.md
index a9677b8..ab345df 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 ## Requirements
 
-* lua >= 5.3
+* lua (versions < 5.3 will have problems displaying non-ASCII characters)
 * curl
 * sed
 * date
diff --git a/c4mate b/c4mate
index 3bcb0d1..29304e0 100755
--- a/c4mate
+++ b/c4mate
@@ -13,6 +13,7 @@ local function utf8_decode(str)
     -- Replace JSON Unicode escape sequences with chars.
     if str == nil then return "" end
     str = string.gsub(str, "\\\"", "\"")
+    if utf8 == nil then return str end -- Only available in Lua >= 5.3.
     return string.gsub(str, "\\u(%x%x%x%x)",
         function (s) return utf8.char(tonumber(s, 16)) end)
 end
@@ -62,7 +63,7 @@ function MatePad:fetch(api, data)
             "curl %s --cookie '%s' --cookie-jar '%s' '%s/%s'",
             self.CURL_FLAGS, self.COOKIE_JAR, self.COOKIE_JAR, self.HOST, api))
     end
-    responce = curl:read("a")
+    responce = curl:read("*a")
 
     ok, exit, signal = curl:close()
     if not ok then
@@ -143,17 +144,17 @@ sed -n '
 
     while true do
         local entry = {}
-        local oldbalance = tonumber(pipe:read("l"))
+        local oldbalance = tonumber(pipe:read("*l"))
         if oldbalance == nil then break end
         entry.oldbalance = oldbalance
-        entry.newbalance = tonumber(pipe:read("l"))
-        entry.parameter = tonumber(pipe:read("l"))
-        entry.method = pipe:read("l")
+        entry.newbalance = tonumber(pipe:read("*l"))
+        entry.parameter = tonumber(pipe:read("*l"))
+        entry.method = pipe:read("*l")
         if entry.method == "buy" or entry.method == "recharge" then
-            entry.name = utf8_decode(pipe:read("l"))
+            entry.name = utf8_decode(pipe:read("*l"))
         else
             -- set_balance, transferTo, transferFrom
-            entry.reason = utf8_decode(pipe:read("l"))
+            entry.reason = utf8_decode(pipe:read("*l"))
         end
         table.insert(log, entry)
     end
@@ -171,7 +172,7 @@ sed -n '
     -- Convert timestamps to local time.
     local timestamps = io.popen("date -f "..datefile.." +'%_c'")
     for i = 1, #log do
-        log[i].time = timestamps:read("l")
+        log[i].time = timestamps:read("*l")
     end
 
     -- Check date exit code.
@@ -248,10 +249,10 @@ sed -n --sandbox '
 
     while true do
         local item = {}
-        item.id = tonumber(pipe:read("l"))
+        item.id = tonumber(pipe:read("*l"))
         if item.id == nil then break end
-        item.name = utf8_decode(pipe:read("l"))
-        item.price = tonumber(pipe:read("l"))
+        item.name = utf8_decode(pipe:read("*l"))
+        item.price = tonumber(pipe:read("*l"))
         table.insert(roster, item)
     end
 
@@ -305,7 +306,7 @@ function MatePad:give(amount, recipient, reason)
         })
 end
 
-
+--
 -- Parse -u flag (which may be given multiple times).
 while arg[1] == "-u" do
     table.remove(arg, 1)
@@ -355,7 +356,8 @@ if arg[1] == nil then
 elseif arg[1] == "-l" or
        arg[1] == "--log" then
     -- Print log.
-    local size = math.max(0, math.tointeger(arg[2]) or 10)
+    local size = tonumber(arg[2]) or 10
+    size = math.max(0, size)
     pad:print_log(pad:parse_log(size))
 
 elseif arg[1] == "-g" or
@@ -405,7 +407,7 @@ elseif tonumber(arg[1]) ~= nil then
     -- Add to (or subtract from) balance.
     pad:init()
     if pad:update_balance() then
-        local new = math.tointeger(pad.balance + tonumber(arg[1])*100)
+        local new = math.floor(pad.balance + tonumber(arg[1])*100)
         if pad:set_balance(new) == "OK" then
             pad:update_balance()
             print(string.format(
@@ -437,8 +439,10 @@ else
     -- Sort menu by id.
     table.sort(menu, function (e1, e2) return e1.id < e2.id end)
 
-    -- Check if we can invoke stty.
-    local is_tty = os.execute("tty -s") == true
+    -- Check if we can invoke stty. Lua5.1 returns 0 on success, later versions
+    -- return true.
+    local is_tty = os.execute("tty -s")
+    is_tty = is_tty == true or is_tty == 0
 
     for i, item in ipairs(menu) do
         io.stdout:write(string.format("[%d/%d] Buy %s (#%d) for %.2f €? ",