diff --git a/cfg.mk b/cfg.mk
index bc8088d7c01dffcb245b262f4d52e04bb2574f12..4aa26d434a20ac9c31603ed6ace3472bdf979185 100644
--- a/cfg.mk
+++ b/cfg.mk
@@ -496,6 +496,7 @@ ctype_re = isalnum|isalpha|isascii|isblank|iscntrl|isdigit|isgraph|islower\
 
 sc_avoid_ctype_macros:
 	@prohibit='\b($(ctype_re)) *\(' \
+	in_vc_files='\.[ch]$$' \
 	halt='use c-ctype.h instead of ctype macros' \
 	  $(_sc_search_regexp)