1 files changed, 1 insertions, 1 deletions
diff --git a/rules.mk b/rules.mk
index d575726c71..9143f9bcff 100644
--- a/rules.mk
+++ b/rules.mk
@@ -317,7 +317,7 @@ GENDEPFLAGS = -MMD -MP -MF .dep/$(@F).d
 
 # Combine all necessary flags and optional flags.
 # Add target processor to flags.
-# You can give EXTRAFLAGS at 'make' command line.
+# You can give extra flags at 'make' command line like: make EXTRAFLAGS=-DFOO=bar
 ALL_CFLAGS = -mmcu=$(MCU) -I. $(CFLAGS) $(GENDEPFLAGS) $(EXTRAFLAGS)
 ALL_CPPFLAGS = -mmcu=$(MCU) -I. -x c++ $(CPPFLAGS) $(GENDEPFLAGS) $(EXTRAFLAGS)
 ALL_ASFLAGS = -mmcu=$(MCU) -I. -x assembler-with-cpp $(ASFLAGS) $(EXTRAFLAGS)