--- a/make/CompileDemos.gmk	Fri Oct 13 14:17:10 2017 +0100
+++ b/make/CompileDemos.gmk	Fri Oct 13 15:22:02 2017 +0200
@@ -37,9 +37,13 @@
 include TextFileProcessing.gmk
 include ZipArchive.gmk
 
+# Hook to include the corresponding custom file, if present.
+$(eval $(call IncludeCustomExtension, CompileDemos-pre.gmk))
+
 # Prepare the find cache.
-$(eval $(call FillCacheFind, $(wildcard $(TOPDIR)/src/demo \
-    $(TOPDIR)/src/*/demo)))
+DEMO_SRC_DIRS += $(TOPDIR)/src/demo
+
+$(eval $(call FillCacheFind, $(wildcard $(DEMO_SRC_DIRS))))
 
 # Append demo goals to this variable.
 TARGETS =
@@ -303,7 +307,7 @@
 
 ################################################################################
 # Hook to include the corresponding custom file, if present.
-$(eval $(call IncludeCustomExtension, CompileDemos.gmk))
+$(eval $(call IncludeCustomExtension, CompileDemos-post.gmk))
 
 all: $(TARGETS)
 images: $(IMAGES_TARGETS)