diff --git a/include/fmt/core.h b/include/fmt/core.h
index f0426093..22768ff8 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -2577,8 +2577,8 @@ FMT_CONSTEXPR auto check_cstring_type_spec(Char spec, ErrorHandler&& eh = {})
   return false;
 }
 
-template <typename Char, typename ErrorHandler>
-FMT_CONSTEXPR void check_string_type_spec(Char spec, ErrorHandler&& eh) {
+template <typename Char, typename ErrorHandler = error_handler>
+FMT_CONSTEXPR void check_string_type_spec(Char spec, ErrorHandler&& eh = {}) {
   if (spec != 0 && spec != 's') eh.on_error("invalid type specifier");
 }
 
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 7de8e98f..0024cf7c 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -1569,6 +1569,7 @@ FMT_CONSTEXPR auto write(OutputIt out,
                          basic_string_view<type_identity_t<Char>> s,
                          const basic_format_specs<Char>& specs, locale_ref)
     -> OutputIt {
+  check_string_type_spec(specs.type);
   return write(out, s, specs);
 }
 template <typename Char, typename OutputIt>
diff --git a/test/format-test.cc b/test/format-test.cc
index 892556f1..ec59a5fc 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1390,6 +1390,8 @@ TEST(format_test, format_pointer) {
 
 TEST(format_test, format_string) {
   EXPECT_EQ("test", fmt::format("{0}", std::string("test")));
+  EXPECT_THROW(fmt::format(fmt::runtime("{:x}"), std::string("test")),
+               fmt::format_error);
 }
 
 TEST(format_test, format_string_view) {