diff --git a/include/fmt/chrono.h b/include/fmt/chrono.h
index 9abe7c4f..ca4ed30a 100644
--- a/include/fmt/chrono.h
+++ b/include/fmt/chrono.h
@@ -696,7 +696,7 @@ inline int to_nonnegative_int(T value, int upper) {
 
 template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
 inline T mod(T x, int y) {
-  return x % y;
+  return x % static_cast<T>(y);
 }
 template <typename T, FMT_ENABLE_IF(std::is_floating_point<T>::value)>
 inline T mod(T x, int y) {
@@ -793,7 +793,10 @@ struct chrono_formatter {
 
   explicit chrono_formatter(FormatContext& ctx, OutputIt o,
                             std::chrono::duration<Rep, Period> d)
-      : context(ctx), out(o), val(d.count()), negative(false) {
+      : context(ctx),
+        out(o),
+        val(static_cast<rep>(d.count())),
+        negative(false) {
     if (d.count() < 0) {
       val = 0 - val;
       negative = true;
@@ -1023,8 +1026,8 @@ struct formatter<std::chrono::duration<Rep, Period>, Char> {
     void on_error(const char* msg) { FMT_THROW(format_error(msg)); }
     void on_fill(Char fill) { f.specs.fill[0] = fill; }
     void on_align(align_t align) { f.specs.align = align; }
-    void on_width(unsigned width) { f.specs.width = width; }
-    void on_precision(unsigned _precision) { f.precision = _precision; }
+    void on_width(int width) { f.specs.width = width; }
+    void on_precision(int _precision) { f.precision = _precision; }
     void end_precision() {}
 
     template <typename Id> void on_dynamic_width(Id arg_id) {
diff --git a/include/fmt/compile.h b/include/fmt/compile.h
index f65f5a74..5829f623 100644
--- a/include/fmt/compile.h
+++ b/include/fmt/compile.h
@@ -26,11 +26,11 @@ template <typename Char> struct format_part {
 
   kind part_kind;
   union value {
-    unsigned arg_index;
+    int arg_index;
     basic_string_view<Char> str;
     replacement repl;
 
-    FMT_CONSTEXPR value(unsigned index = 0) : arg_index(index) {}
+    FMT_CONSTEXPR value(int index = 0) : arg_index(index) {}
     FMT_CONSTEXPR value(basic_string_view<Char> s) : str(s) {}
     FMT_CONSTEXPR value(replacement r) : repl(r) {}
   } val;
@@ -40,7 +40,7 @@ template <typename Char> struct format_part {
   FMT_CONSTEXPR format_part(kind k = kind::arg_index, value v = {})
       : part_kind(k), val(v) {}
 
-  static FMT_CONSTEXPR format_part make_arg_index(unsigned index) {
+  static FMT_CONSTEXPR format_part make_arg_index(int index) {
     return format_part(kind::arg_index, index);
   }
   static FMT_CONSTEXPR format_part make_arg_name(basic_string_view<Char> name) {
@@ -62,7 +62,7 @@ template <typename Char> struct part_counter {
   }
 
   FMT_CONSTEXPR void on_arg_id() { ++num_parts; }
-  FMT_CONSTEXPR void on_arg_id(unsigned) { ++num_parts; }
+  FMT_CONSTEXPR void on_arg_id(int) { ++num_parts; }
   FMT_CONSTEXPR void on_arg_id(basic_string_view<Char>) { ++num_parts; }
 
   FMT_CONSTEXPR void on_replacement_field(const Char*) {}
@@ -119,7 +119,7 @@ class format_string_compiler : public error_handler {
     part_ = part::make_arg_index(parse_context_.next_arg_id());
   }
 
-  FMT_CONSTEXPR void on_arg_id(unsigned id) {
+  FMT_CONSTEXPR void on_arg_id(int id) {
     parse_context_.check_arg_id(id);
     part_ = part::make_arg_index(id);
   }
@@ -512,8 +512,6 @@ template <typename CompiledFormat, typename... Args,
                                          CompiledFormat>::value)>
 std::basic_string<Char> format(const CompiledFormat& cf, const Args&... args) {
   basic_memory_buffer<Char> buffer;
-  using range = buffer_range<Char>;
-  using context = buffer_context<Char>;
   cf.format(std::back_inserter(buffer), args...);
   return to_string(buffer);
 }
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 46ada8d6..01f41f5c 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -2567,7 +2567,7 @@ class format_string_checker {
  public:
   explicit FMT_CONSTEXPR format_string_checker(
       basic_string_view<Char> format_str, ErrorHandler eh)
-      : arg_id_(max_value<unsigned>()),
+      : arg_id_(-1),
         context_(format_str, eh),
         parse_funcs_{&parse_format_specs<Args, parse_context_type>...} {}
 
@@ -2608,7 +2608,7 @@ class format_string_checker {
   // Format specifier parsing function.
   using parse_func = const Char* (*)(parse_context_type&);
 
-  unsigned arg_id_;
+  int arg_id_;
   parse_context_type context_;
   parse_func parse_funcs_[num_args > 0 ? num_args : 1];
 };
diff --git a/include/fmt/printf.h b/include/fmt/printf.h
index cdbb65e6..a2fa945d 100644
--- a/include/fmt/printf.h
+++ b/include/fmt/printf.h
@@ -333,12 +333,12 @@ template <typename OutputIt, typename Char> class basic_printf_context {
   static void parse_flags(format_specs& specs, const Char*& it,
                           const Char* end);
 
-  // Returns the argument with specified index or, if arg_index is equal
-  // to the maximum unsigned value, the next argument.
-  format_arg get_arg(unsigned arg_index = internal::max_value<unsigned>());
+  // Returns the argument with specified index or, if arg_index is -1, the next
+  // argument.
+  format_arg get_arg(int arg_index = -1);
 
   // Parses argument index, flags and width and returns the argument index.
-  unsigned parse_header(const Char*& it, const Char* end, format_specs& specs);
+  int parse_header(const Char*& it, const Char* end, format_specs& specs);
 
  public:
   /**
@@ -355,7 +355,7 @@ template <typename OutputIt, typename Char> class basic_printf_context {
   OutputIt out() { return out_; }
   void advance_to(OutputIt it) { out_ = it; }
 
-  format_arg arg(unsigned id) const { return args_.get(id); }
+  format_arg arg(int id) const { return args_.get(id); }
 
   basic_format_parse_context<Char>& parse_context() { return parse_ctx_; }
 
@@ -397,8 +397,8 @@ void basic_printf_context<OutputIt, Char>::parse_flags(format_specs& specs,
 
 template <typename OutputIt, typename Char>
 typename basic_printf_context<OutputIt, Char>::format_arg
-basic_printf_context<OutputIt, Char>::get_arg(unsigned arg_index) {
-  if (arg_index == internal::max_value<unsigned>())
+basic_printf_context<OutputIt, Char>::get_arg(int arg_index) {
+  if (arg_index < 0)
     arg_index = parse_ctx_.next_arg_id();
   else
     parse_ctx_.check_arg_id(--arg_index);
@@ -406,15 +406,15 @@ basic_printf_context<OutputIt, Char>::get_arg(unsigned arg_index) {
 }
 
 template <typename OutputIt, typename Char>
-unsigned basic_printf_context<OutputIt, Char>::parse_header(
+int basic_printf_context<OutputIt, Char>::parse_header(
     const Char*& it, const Char* end, format_specs& specs) {
-  unsigned arg_index = internal::max_value<unsigned>();
+  int arg_index = -1;
   char_type c = *it;
   if (c >= '0' && c <= '9') {
     // Parse an argument index (if followed by '$') or a width possibly
     // preceded with '0' flag(s).
     internal::error_handler eh;
-    unsigned value = parse_nonnegative_int(it, end, eh);
+    int value = parse_nonnegative_int(it, end, eh);
     if (it != end && *it == '$') {  // value is an argument index
       ++it;
       arg_index = value;
@@ -436,8 +436,8 @@ unsigned basic_printf_context<OutputIt, Char>::parse_header(
       specs.width = parse_nonnegative_int(it, end, eh);
     } else if (*it == '*') {
       ++it;
-      specs.width = visit_format_arg(
-          internal::printf_width_handler<char_type>(specs), get_arg());
+      specs.width = static_cast<int>(visit_format_arg(
+          internal::printf_width_handler<char_type>(specs), get_arg()));
     }
   }
   return arg_index;
@@ -464,7 +464,7 @@ OutputIt basic_printf_context<OutputIt, Char>::format() {
     specs.align = align::right;
 
     // Parse argument index, flags and width.
-    unsigned arg_index = parse_header(it, end, specs);
+    int arg_index = parse_header(it, end, specs);
     if (arg_index == 0) on_error("argument index out of range");
 
     // Parse precision.
@@ -473,11 +473,11 @@ OutputIt basic_printf_context<OutputIt, Char>::format() {
       c = it != end ? *it : 0;
       if ('0' <= c && c <= '9') {
         internal::error_handler eh;
-        specs.precision = static_cast<int>(parse_nonnegative_int(it, end, eh));
+        specs.precision = parse_nonnegative_int(it, end, eh);
       } else if (c == '*') {
         ++it;
         specs.precision =
-            visit_format_arg(internal::printf_precision_handler(), get_arg());
+            static_cast<int>(visit_format_arg(internal::printf_precision_handler(), get_arg()));
       } else {
         specs.precision = 0;
       }