diff --git a/gtsam/base/SymmetricBlockMatrix.h b/gtsam/base/SymmetricBlockMatrix.h
index da3a9a8b8..53a8912f6 100644
--- a/gtsam/base/SymmetricBlockMatrix.h
+++ b/gtsam/base/SymmetricBlockMatrix.h
@@ -24,7 +24,7 @@
 #include <boost/serialization/nvp.hpp>
 #include <cassert>
 #include <stdexcept>
-#include <vector>
+#include <array>
 
 namespace boost {
 namespace serialization {