diff --git a/cfg.mk b/cfg.mk
index 680c31260658674714bd18c214418940005651ac..8b89cd217d441cf33629ffefe5b2d6f9efcc4d1b 100644
--- a/cfg.mk
+++ b/cfg.mk
@@ -251,6 +251,19 @@ sc_prohibit_trailing_blank_lines:
 	rm -f $@-t;							\
 	test $$found = 0
 
+# Regex for grep -E that exempts generated files from style rules.
+preprocessor_exempt = (remote_(driver|protocol)\.h)$$
+# Enforce recommended preprocessor indentation style.
+sc_preprocessor_indentation:
+	@if (cppi --version >/dev/null 2>&1); then			\
+	  $(VC_LIST_EXCEPT) | grep '\.[ch]$$'				\
+	    | grep -vE '$(preprocessor_exempt)' | xargs cppi -a -c	\
+	    || { echo '$(ME): incorrect preprocessor indentation' 1>&2;	\
+		exit 1; };						\
+	else								\
+	  echo '$(ME): skipping test $@: cppi not installed' 1>&2;	\
+	fi
+
 # We don't use this feature of maint.mk.
 prev_version_file = /dev/null