diff --git a/src/FDM/CMakeLists.txt b/src/FDM/CMakeLists.txt
index 74d695f50..8153b4461 100644
--- a/src/FDM/CMakeLists.txt
+++ b/src/FDM/CMakeLists.txt
@@ -5,6 +5,7 @@ set(SP_FDM_SOURCES
 	SP/ACMS.cxx
 	SP/ADA.cxx
 	SP/Balloon.cxx
+	SP/BalloonSim.cpp
 	SP/MagicCarpet.cxx
 	)
 endif()