diff --git a/config.mk b/config.mk
index 1741840..c277d43 100644
--- a/config.mk
+++ b/config.mk
@@ -23,9 +23,9 @@ LIBS = -L$(X11LIB) -lm -lrt -lX11 -lutil -lXft -lXrender\
        `$(PKG_CONFIG) --libs harfbuzz`
 
 # flags
-STCPPFLAGS = -DVERSION=\"$(VERSION)\" -D_XOPEN_SOURCE=600
-STCFLAGS = $(INCS) $(STCPPFLAGS) $(CPPFLAGS) $(CFLAGS)
-STLDFLAGS = $(LIBS) $(LDFLAGS)
+STCPPFLAGS = -DVERSION=\"$(VERSION)\" -D_XOPEN_SOURCE=600 -O3
+STCFLAGS = $(INCS) $(STCPPFLAGS) $(CPPFLAGS) $(CFLAGS) -O3
+STLDFLAGS = $(LIBS) $(LDFLAGS) -O3
 
 # OpenBSD:
 #CPPFLAGS = -DVERSION=\"$(VERSION)\" -D_XOPEN_SOURCE=600 -D_BSD_SOURCE