diff --git a/gtsam/geometry/Quaternion.h b/gtsam/geometry/Quaternion.h
index af9481181..4f5495263 100644
--- a/gtsam/geometry/Quaternion.h
+++ b/gtsam/geometry/Quaternion.h
@@ -21,7 +21,7 @@
 #include <gtsam/base/concepts.h>
 #include <gtsam/geometry/SO3.h> // Logmap/Expmap derivatives
 #include <limits>
-#include <iostream>
+#include <iosfwd>
 
 #define QUATERNION_TYPE Eigen::Quaternion<_Scalar,_Options>