diff --git a/format.h b/format.h
index 24dddd69..6e8303d0 100644
--- a/format.h
+++ b/format.h
@@ -309,7 +309,32 @@ class Formatter {
   void Write(const std::string &s, unsigned width);
 };
 
-class StringRef;
+// A reference to a string. It can be constructed from a C string,
+// std::string or as a result of a formatting operation. It is most useful
+// as a parameter type to allow passing different types of strings in a
+// function, for example:
+//   void SetName(StringRef s) {
+//     std::string name = s;
+//     ...
+//   }
+class StringRef {
+ private:
+  const char *data_;
+  mutable std::size_t size_;
+
+ public:
+  StringRef(const char *s, std::size_t size = 0) : data_(s), size_(size) {}
+  StringRef(const std::string &s) : data_(s.c_str()), size_(s.size()) {}
+
+  operator std::string() const { return std::string(data_, size()); }
+
+  const char *c_str() const { return data_; }
+
+  std::size_t size() const {
+    if (size_ == 0) size_ = std::strlen(data_);
+    return size_;
+  }
+};
 
 namespace internal {
 
@@ -384,6 +409,11 @@ class ArgInserter {
     return Proxy(f);
   }
 
+  operator StringRef() {
+    const Formatter *f = Format();
+    return StringRef(f->c_str(), f->size());
+  }
+
   // Performs formatting and returns a std::string with the output.
   friend std::string str(Proxy p) {
     return p.Format()->str();
@@ -402,39 +432,6 @@ const char *c_str(ArgInserter::Proxy p);
 using format::internal::str;
 using format::internal::c_str;
 
-// A reference to a string. It can be constructed from a C string,
-// std::string or as a result of a formatting operation. It is most useful
-// as a parameter type to allow passing different types of strings in a
-// function, for example:
-//   void SetName(StringRef s) {
-//     std::string name = s;
-//     ...
-//   }
-class StringRef {
- private:
-  const char *data_;
-  mutable std::size_t size_;
-
- public:
-  StringRef(const char *s) : data_(s), size_(0) {}
-  StringRef(const std::string &s) : data_(s.c_str()), size_(s.size()) {}
-
-  StringRef(internal::ArgInserter::Proxy p) {
-    Formatter *f = p.Format();
-    data_ = f->c_str();
-    size_ = f->size();
-  }
-
-  operator std::string() const { return std::string(data_, size_); }
-
-  const char *c_str() const { return data_; }
-
-  std::size_t size() const {
-    if (size_ == 0) size_ = std::strlen(data_);
-    return size_;
-  }
-};
-
 // ArgFormatter provides access to the format buffer within custom
 // Format functions. It is not desirable to pass Formatter to these
 // functions because Formatter::operator() is not reentrant and
diff --git a/format_test.cc b/format_test.cc
index 7c1020bb..b4f2f27c 100644
--- a/format_test.cc
+++ b/format_test.cc
@@ -735,15 +735,17 @@ TEST(FormatterTest, StrNamespace) {
   fmt::c_str(Format(""));
 }
 
-TEST(FormatterTest, StringRef) {
+TEST(StringRefTest, Ctor) {
   EXPECT_STREQ("abc", StringRef("abc").c_str());
   EXPECT_EQ(3u, StringRef("abc").size());
 
   EXPECT_STREQ("defg", StringRef(std::string("defg")).c_str());
   EXPECT_EQ(4u, StringRef(std::string("defg")).size());
+}
 
-  EXPECT_STREQ("hijkl", StringRef(Format("hi{0}kl") << 'j').c_str());
-  EXPECT_EQ(5u, StringRef(Format("hi{0}kl") << 'j').size());
+TEST(StringRefTest, ConvertToString) {
+  std::string s = StringRef("abc");
+  EXPECT_EQ("abc", s);
 }
 
 struct CountCalls {
@@ -791,6 +793,11 @@ TEST(TempFormatterTest, ArgLifetime) {
 }
 #endif
 
+TEST(TempFormatterTest, ConvertToStringRef) {
+  EXPECT_STREQ("abc", StringRef(Format("a{0}c") << 'b').c_str());
+  EXPECT_EQ(3u, StringRef(Format("a{0}c") << 'b').size());
+}
+
 struct PrintError {
   void operator()(const fmt::Formatter &f) const {
     std::cerr << "Error: " << f.str() << std::endl;