diff --git a/Makefile b/Makefile
index 20121e0..c0a65b7 100644
--- a/Makefile
+++ b/Makefile
@@ -7,6 +7,7 @@ SOURCES=Coord.cpp \
 	Julian.cpp \
 	Observer.cpp \
 	SGDP4.cpp \
+        Timespan.cpp \
 	Tle.cpp \
 	Vector.cpp  \
 	main.cpp