diff --git a/mk/suffix.mk b/mk/suffix.mk
index d16513fad37590f99ea7f6b02cffaae5a5ee531b..69d164e94cdece084c256a420ba36108b0ca7d84 100644
--- a/mk/suffix.mk
+++ b/mk/suffix.mk
@@ -146,6 +146,7 @@ endif
 #-----------------------------------------------------------------------------
 # C-related suffix rules
 
+# UseGhcForCc is only relevant when not booting from HC files.
 ifeq "$(UseGhcForCc) $(BootingFromHc)" "YES NO"
 
 $(odir_)%.$(way_)o : %.c