diff --git a/Makefile b/Makefile
index d62b121..726515c 100644
--- a/Makefile
+++ b/Makefile
@@ -6,7 +6,7 @@ TARGET = ace
 PREFIX ?= /usr/local
 BINDIR = $(PREFIX)/bin
 
-CFLAGS = -O3 -march=native -mtune=native -pipe -s -std=c99 -flto -pedantic -Wall
+CFLAGS = -Os -march=native -mtune=native -pipe -s -std=c99 -flto -pedantic -Wall
 
 SRC = ace.c
 
diff --git a/ace.c b/ace.c
index 07b12e2..74c9f5a 100644
--- a/ace.c
+++ b/ace.c
@@ -13,13 +13,13 @@ typedef struct {
 	int suit; /* 0 to 3 (Hearts, Spades, Diamonds, Clubs) */
 } card;
 
-card deal_card();
+card deal_card(void);
 int calculate_score(card hand[], int num_cards);
 void display_hand(card hand[], int num_cards, int is_player, int total);
 
 struct termios orig_termios;
 
-int main()
+int main(void)
 {
 	srand(time(NULL));
 
@@ -111,7 +111,7 @@ int main()
 	return 0;
 }
 
-card deal_card()
+card deal_card(void)
 {
 	card card;
 	card.value = rand() % 13 + 1;