diff --git a/media/baseset/openttd/CMakeLists.txt b/media/baseset/openttd/CMakeLists.txt
new file mode 100644
--- /dev/null
+++ b/media/baseset/openttd/CMakeLists.txt
@@ -0,0 +1,9 @@
+# In case both NFORenum and GRFCodec are found, generate the GRF.
+# Otherwise, just use them from the cache (read: git).
+# This is mainly because not many people have both of these tools installed,
+# so it is cheaper to cache them in git, and only regenerate when you are
+# working on it / have the tools installed.
+if (NFORENUM_FOUND AND GRFCODEC_FOUND)
+    include(CreateGrfCommand REQUIRED)
+    create_grf_command()
+endif (NFORENUM_FOUND AND GRFCODEC_FOUND)