diff --git a/gtsam/inference/Key.h b/gtsam/inference/Key.h
index 8b13f0b4ca..2cc19d07a5 100644
--- a/gtsam/inference/Key.h
+++ b/gtsam/inference/Key.h
@@ -25,14 +25,14 @@
 #include <gtsam/base/types.h>
 #include <gtsam/dllexport.h>
 
-#include <boost/function.hpp>
+#include <functional>
 
 #include <iosfwd>
 
 namespace gtsam {
 
 /// Typedef for a function to format a key, i.e. to convert it to a string
-typedef boost::function<std::string(Key)> KeyFormatter;
+typedef std::function<std::string(Key)> KeyFormatter;
 
 // Helper function for DefaultKeyFormatter
 GTSAM_EXPORT std::string _defaultKeyFormatter(Key key);
diff --git a/gtsam/inference/LabeledSymbol.h b/gtsam/inference/LabeledSymbol.h
index d46425bb48..15a2a25014 100644
--- a/gtsam/inference/LabeledSymbol.h
+++ b/gtsam/inference/LabeledSymbol.h
@@ -20,6 +20,7 @@
 #pragma once
 
 #include <gtsam/inference/Symbol.h>
+#include <boost/function.hpp>
 
 namespace gtsam {
 
diff --git a/gtsam/inference/Symbol.h b/gtsam/inference/Symbol.h
index d5699e7fed..89fb0d161e 100644
--- a/gtsam/inference/Symbol.h
+++ b/gtsam/inference/Symbol.h
@@ -21,6 +21,7 @@
 #include <gtsam/inference/Key.h>
 #include <gtsam/base/Testable.h>
 #include <boost/serialization/nvp.hpp>
+#include <boost/function.hpp>
 #include <cstdint>
 
 namespace gtsam {