diff --git a/CMakeLists.txt b/CMakeLists.txt
index bf5c7e7e2c..ff3a62ed01 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -193,6 +193,8 @@ px4_add_git_submodule(TARGET git_cmake_hexagon PATH "cmake/cmake_hexagon")
 px4_add_git_submodule(TARGET git_driverframework PATH "src/lib/DriverFramework")
 px4_add_git_submodule(TARGET git_ecl PATH "src/lib/ecl")
 px4_add_git_submodule(TARGET git_gazebo PATH "Tools/sitl_gazebo")
+px4_add_git_submodule(TARGET git_gazebo_flow PATH "Tools/sitl_gazebo/external/OpticalFlow")
+px4_add_git_submodule(TARGET git_gazebo_klt PATH "Tools/sitl_gazebo/external/OpticalFlow/external/klt_feature_tracker")
 px4_add_git_submodule(TARGET git_gencpp PATH "Tools/gencpp")
 px4_add_git_submodule(TARGET git_genmsg PATH "Tools/genmsg")
 px4_add_git_submodule(TARGET git_gps_devices PATH "src/drivers/gps/devices")