diff --git a/format.h b/format.h
index a7b8658d..4ad33cd6 100644
--- a/format.h
+++ b/format.h
@@ -518,6 +518,7 @@ class UTF8ToUTF16 {
   explicit UTF8ToUTF16(StringRef s);
   operator WStringRef() const { return WStringRef(&buffer_[0], size()); }
   size_t size() const { return buffer_.size() - 1; }
+  std::wstring() const { return std::wstring(&buffer_[0], size()); }
 };
 
 // A converter from UTF-16 to UTF-8.
@@ -531,6 +532,7 @@ class UTF16ToUTF8 {
   explicit UTF16ToUTF8(WStringRef s);
   operator StringRef() const { return StringRef(&buffer_[0], size()); }
   size_t size() const { return buffer_.size() - 1; }
+  std::string() const { return std::string(&buffer_[0], size()); }
 
   // Performs conversion returning a system error code instead of
   // throwing exception on error.
diff --git a/test/util-test.cc b/test/util-test.cc
index 65f82522..becd9ff1 100644
--- a/test/util-test.cc
+++ b/test/util-test.cc
@@ -92,14 +92,14 @@ TEST(UtilTest, CountDigits) {
 TEST(UtilTest, UTF16ToUTF8) {
   std::string s = "ёжик";
   fmt::internal::UTF16ToUTF8 u(L"\x0451\x0436\x0438\x043A");
-  EXPECT_EQ(s, fmt::str(u));
+  EXPECT_EQ(s, u.str());
   EXPECT_EQ(s.size(), u.size());
 }
 
 TEST(UtilTest, UTF8ToUTF16) {
   std::string s = "лошадка";
   fmt::internal::UTF8ToUTF16 u(s.c_str());
-  EXPECT_EQ(L"\x043B\x043E\x0448\x0430\x0434\x043A\x0430", fmt::str(u));
+  EXPECT_EQ(L"\x043B\x043E\x0448\x0430\x0434\x043A\x0430", u.str());
   EXPECT_EQ(7, u.size());
 }