diff --git a/src/SdLine.hpp b/src/SdLine.hpp
index 531a478..8b1046d 100644
--- a/src/SdLine.hpp
+++ b/src/SdLine.hpp
@@ -5,6 +5,7 @@
 #include <chrono>
 #include <string>
 #include <utility>
+#include <iosfwd>
 
 
 namespace jess