diff --git a/Makefile b/Makefile
index fb80529..e0a7510 100644
--- a/Makefile
+++ b/Makefile
@@ -59,7 +59,7 @@
 # that lacks some of the necessary tools to re-generate the files.
 # If $(GEN_FILES) is non-empty, the generated source files' dependencies
 # are treated ordinarily, based on file timestamps.
-GEN_FILES ?= yes
+GEN_FILES ?=
 
 # In dependencies where the target is a configuration-independent generated
 # file, use `TARGET: $(gen_file_dep) DEPENDENCY1 DEPENDENCY2 ...`