diff --git a/include/fmt/core.h b/include/fmt/core.h
index d71a2ab1..db52c5e6 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -87,7 +87,7 @@
 // GCC doesn't allow throw in constexpr until version 6 (bug 67371).
 #ifndef FMT_USE_CONSTEXPR
 #  define FMT_USE_CONSTEXPR                                           \
-    (FMT_HAS_FEATURE(cxx_relaxed_constexpr) || FMT_MSC_VER >= 1920 || \
+    (FMT_HAS_FEATURE(cxx_relaxed_constexpr) || FMT_MSC_VER >= 1910 || \
      (FMT_GCC_VERSION >= 600 && __cplusplus >= 201402L)) &&           \
         !FMT_NVCC && !FMT_ICC_VERSION
 #endif
@@ -1581,7 +1581,7 @@ template <typename OutputIt, typename Char> class basic_format_context {
   FMT_CONSTEXPR auto arg(basic_string_view<char_type> name) -> format_arg {
     return args_.get(name);
   }
-  auto arg_id(basic_string_view<char_type> name) -> int {
+  FMT_CONSTEXPR auto arg_id(basic_string_view<char_type> name) -> int {
     return args_.get_id(name);
   }
   auto args() const -> const basic_format_args<basic_format_context>& {
@@ -2179,7 +2179,7 @@ FMT_CONSTEXPR auto parse_width(const Char* begin, const Char* end,
       handler.on_dynamic_width(id);
     }
     FMT_CONSTEXPR void on_error(const char* message) {
-      handler.on_error(message);
+      if (message) handler.on_error(message);
     }
   };
 
@@ -2209,7 +2209,7 @@ FMT_CONSTEXPR auto parse_precision(const Char* begin, const Char* end,
       handler.on_dynamic_precision(id);
     }
     FMT_CONSTEXPR void on_error(const char* message) {
-      handler.on_error(message);
+      if (message) handler.on_error(message);
     }
   };
 
@@ -2310,7 +2310,7 @@ FMT_CONSTEXPR auto parse_replacement_field(const Char* begin, const Char* end,
       arg_id = handler.on_arg_id(id);
     }
     FMT_CONSTEXPR void on_error(const char* message) {
-      handler.on_error(message);
+      if (message) handler.on_error(message);
     }
   };
 
diff --git a/include/fmt/format.h b/include/fmt/format.h
index b03449e1..58122935 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -2659,9 +2659,11 @@ void vformat_to(buffer<Char>& buf, basic_string_view<Char> fmt,
       context.advance_to(write<Char>(context.out(), text));
     }
 
-    int on_arg_id() { return parse_context.next_arg_id(); }
-    int on_arg_id(int id) { return parse_context.check_arg_id(id), id; }
-    int on_arg_id(basic_string_view<Char> id) {
+    FMT_CONSTEXPR int on_arg_id() { return parse_context.next_arg_id(); }
+    FMT_CONSTEXPR int on_arg_id(int id) {
+      return parse_context.check_arg_id(id), id;
+    }
+    FMT_CONSTEXPR int on_arg_id(basic_string_view<Char> id) {
       int arg_id = context.arg_id(id);
       if (arg_id < 0) on_error("argument not found");
       return arg_id;
diff --git a/test/scan.h b/test/scan.h
index de82067a..41748ae8 100644
--- a/test/scan.h
+++ b/test/scan.h
@@ -169,13 +169,16 @@ struct scan_handler : error_handler {
     scan_ctx_.advance_to(it + size);
   }
 
-  int on_arg_id() { return on_arg_id(next_arg_id_++); }
-  int on_arg_id(int id) {
+  FMT_CONSTEXPR int on_arg_id() { return on_arg_id(next_arg_id_++); }
+  FMT_CONSTEXPR int on_arg_id(int id) {
     if (id >= args_.size) on_error("argument index out of range");
     arg_ = args_.data[id];
     return id;
   }
-  int on_arg_id(string_view) { return on_error("invalid format"), 0; }
+  FMT_CONSTEXPR int on_arg_id(string_view id) {
+    if (id.data()) on_error("invalid format");
+    return 0;
+  }
 
   void on_replacement_field(int, const char*) {
     auto it = scan_ctx_.begin(), end = scan_ctx_.end();