diff --git a/gtsam/inference/Symbol.cpp b/gtsam/inference/Symbol.cpp
index ccabcb07e..5e41b3eac 100644
--- a/gtsam/inference/Symbol.cpp
+++ b/gtsam/inference/Symbol.cpp
@@ -66,5 +66,10 @@ boost::function<bool(Key)> Symbol::ChrTest(unsigned char c) {
   return bind(&Symbol::chr, bind(make, _1)) == c;
 }
 
+std::ostream &operator<<(std::ostream &os, const Symbol &symbol) {
+  os << StreamedKey(symbol);
+  return os;
+}
+
 } // namespace gtsam
 
diff --git a/gtsam/inference/Symbol.h b/gtsam/inference/Symbol.h
index 8e22202ed..86574f70d 100644
--- a/gtsam/inference/Symbol.h
+++ b/gtsam/inference/Symbol.h
@@ -112,6 +112,9 @@ public:
    */
   static boost::function<bool(Key)> ChrTest(unsigned char c);
 
+  /// Output stream operator that can be used with key_formatter (see Key.h).
+  friend std::ostream &operator<<(std::ostream &, const Symbol &);
+
 private:
 
   /** Serialization function */
diff --git a/gtsam/inference/tests/testSymbol.cpp b/gtsam/inference/tests/testSymbol.cpp
new file mode 100644
index 000000000..43a0e219a
--- /dev/null
+++ b/gtsam/inference/tests/testSymbol.cpp
@@ -0,0 +1,50 @@
+/* ----------------------------------------------------------------------------
+
+ * GTSAM Copyright 2010, Georgia Tech Research Corporation,
+ * Atlanta, Georgia 30332-0415
+ * All Rights Reserved
+ * Authors: Frank Dellaert, et al. (see THANKS for the full author list)
+
+ * See LICENSE for the license information
+
+ * -------------------------------------------------------------------------- */
+
+/*
+ * @file testSymbol.cpp
+ * @author Frank Dellaert
+ */
+
+#include <gtsam/inference/Symbol.h>
+
+#include <CppUnitLite/TestHarness.h>
+
+using namespace std;
+using namespace gtsam;
+
+/* ************************************************************************* */
+// A custom (nonsensical) formatter.
+string myFormatter(Key key) {
+  return "special";
+}
+
+TEST(Symbol, Formatting) {
+  Symbol symbol('c', 3);
+
+  // use key_formatter with a function pointer
+  stringstream ss2;
+  ss2 << key_formatter(myFormatter) << symbol;
+  EXPECT("special" == ss2.str());
+
+  // use key_formatter with a function object.
+  stringstream ss3;
+  ss3 << key_formatter(MultiRobotKeyFormatter) << symbol;
+  EXPECT("c3" == ss3.str());
+}
+
+/* ************************************************************************* */
+int main() {
+  TestResult tr;
+  return TestRegistry::runAllTests(tr);
+}
+/* ************************************************************************* */
+