diff --git a/simgear/scene/sky/clouds3d/Makefile.am b/simgear/scene/sky/clouds3d/Makefile.am
index 9c8ff6f4..9b492a4a 100644
--- a/simgear/scene/sky/clouds3d/Makefile.am
+++ b/simgear/scene/sky/clouds3d/Makefile.am
@@ -28,3 +28,5 @@ libsgclouds3d_a_SOURCES = \
 	SkyContext.cpp \
 	SkySceneManager.cpp \
 	SkySceneLoader.cpp
+
+INCLUDES = -I$(top_srcdir)