diff --git a/gtsam/inference/LabeledSymbol.cpp b/gtsam/inference/LabeledSymbol.cpp
index 6d34883fa..e67c56e5e 100644
--- a/gtsam/inference/LabeledSymbol.cpp
+++ b/gtsam/inference/LabeledSymbol.cpp
@@ -123,7 +123,7 @@ boost::function<bool(gtsam::Key)> LabeledSymbol::TypeLabelTest(unsigned char c,
 }
 
 /* ************************************************************************* */
-std::ostream &operator<<(std::ostream &os, const LabeledSymbol &symbol) {
+GTSAM_EXPORT std::ostream &operator<<(std::ostream &os, const LabeledSymbol &symbol) {
   os << StreamedKey(symbol);
   return os;
 }
diff --git a/gtsam/inference/LabeledSymbol.h b/gtsam/inference/LabeledSymbol.h
index 5b3ec8766..d46425bb4 100644
--- a/gtsam/inference/LabeledSymbol.h
+++ b/gtsam/inference/LabeledSymbol.h
@@ -107,7 +107,7 @@ public:
   LabeledSymbol newLabel(unsigned char label) const { return LabeledSymbol(c_, label, j_); }
 
   /// Output stream operator that can be used with key_formatter (see Key.h).
-  friend std::ostream &operator<<(std::ostream &, const LabeledSymbol &);
+  friend GTSAM_EXPORT std::ostream &operator<<(std::ostream &, const LabeledSymbol &);
 
 private: