diff --git a/include/fmt/format.h b/include/fmt/format.h
index 751a1594..1093bb5b 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -1205,7 +1205,7 @@ class value {
     custom_value<char_type> custom;
   };
 
-  constexpr value() {}
+  constexpr value() : int_value(0) {}
   value(bool val) { set<BOOL>(int_value, val); }
   value(short val) { set<INT>(int_value, val); }
   value(unsigned short val) { set<UINT>(uint_value, val); }
@@ -3267,7 +3267,7 @@ struct arg_ref {
   enum Kind { NONE, INDEX, NAME };
 
   constexpr arg_ref() : kind(NONE), index(0) {}
-  explicit arg_ref(unsigned index) : kind(INDEX), index(index) {}
+  constexpr explicit arg_ref(unsigned index) : kind(INDEX), index(index) {}
   explicit arg_ref(basic_string_view<Char> name) : kind(NAME), name(name) {}
 
   constexpr arg_ref &operator=(unsigned index) {
@@ -3300,17 +3300,17 @@ class dynamic_specs_handler :
  public:
   using char_type = typename ParseContext::char_type;
 
-  dynamic_specs_handler(
+  constexpr dynamic_specs_handler(
       dynamic_format_specs<char_type> &specs, ParseContext &ctx)
     : specs_setter<char_type>(specs), specs_(specs), context_(ctx) {}
 
   template <typename Id>
-  void on_dynamic_width(Id arg_id) {
+  constexpr void on_dynamic_width(Id arg_id) {
     specs_.width_ref = make_arg_ref(arg_id);
   }
 
   template <typename Id>
-  void on_dynamic_precision(Id arg_id) {
+  constexpr void on_dynamic_precision(Id arg_id) {
     specs_.precision_ref = make_arg_ref(arg_id);
   }
 
@@ -3318,12 +3318,12 @@ class dynamic_specs_handler :
   using arg_ref_type = arg_ref<char_type>;
 
   template <typename Id>
-  arg_ref_type make_arg_ref(Id arg_id) {
+  constexpr arg_ref_type make_arg_ref(Id arg_id) {
     context_.check_arg_id(arg_id);
     return arg_ref_type(arg_id);
   }
 
-  arg_ref_type make_arg_ref(auto_id) {
+  constexpr arg_ref_type make_arg_ref(auto_id) {
     const char *error = 0;
     auto index = context_.next_arg_index(error);
     if (error)
diff --git a/test/format-test.cc b/test/format-test.cc
index 48f6c439..e9826d38 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1693,6 +1693,8 @@ struct test_context {
 
   template <typename Id>
   constexpr void check_arg_id(Id) {}
+
+  constexpr unsigned next_arg_index(const char *&) { return 33; }
 };
 
 constexpr fmt::format_specs parse_specs(const char *s) {
@@ -1719,3 +1721,29 @@ TEST(FormatTest, ConstexprSpecsHandler) {
   static_assert(parse_specs(".{0}").precision() == 22, "");
   static_assert(parse_specs("d").type() == 'd', "");
 }
+
+constexpr fmt::internal::dynamic_format_specs<char>
+    parse_dynamic_specs(const char *s) {
+  fmt::internal::dynamic_format_specs<char> specs;
+  test_context ctx;
+  fmt::internal::dynamic_specs_handler<test_context> h(specs, ctx);
+  parse_format_specs(s, h);
+  return specs;
+}
+
+TEST(FormatTest, ConstexprDynamicSpecsHandler) {
+  static_assert(parse_dynamic_specs("<").align() == fmt::ALIGN_LEFT, "");
+  static_assert(parse_dynamic_specs("*^").fill() == '*', "");
+  static_assert(parse_dynamic_specs("+").flag(fmt::PLUS_FLAG), "");
+  static_assert(parse_dynamic_specs("-").flag(fmt::MINUS_FLAG), "");
+  static_assert(parse_dynamic_specs(" ").flag(fmt::SIGN_FLAG), "");
+  static_assert(parse_dynamic_specs("#").flag(fmt::HASH_FLAG), "");
+  static_assert(parse_dynamic_specs("0").align() == fmt::ALIGN_NUMERIC, "");
+  static_assert(parse_dynamic_specs("42").width() == 42, "");
+  static_assert(parse_dynamic_specs("{}").width_ref.index == 33, "");
+  static_assert(parse_dynamic_specs("{42}").width_ref.index == 42, "");
+  static_assert(parse_dynamic_specs(".42").precision() == 42, "");
+  static_assert(parse_dynamic_specs(".{}").precision_ref.index == 33, "");
+  static_assert(parse_dynamic_specs(".{42}").precision_ref.index == 42, "");
+  static_assert(parse_dynamic_specs("d").type() == 'd', "");
+}