diff --git a/board/bf548-ezkit/config.mk b/board/bf548-ezkit/config.mk
index 7f38b14..ab3ff14 100644
--- a/board/bf548-ezkit/config.mk
+++ b/board/bf548-ezkit/config.mk
@@ -25,6 +25,7 @@
 
 CFLAGS_lib += -O2
 CFLAGS_lib/lzma += -O2
+CFLAGS_lib/zlib += -O2
 
 # Set some default LDR flags based on boot mode.
 LDR_FLAGS-BFIN_BOOT_PARA       := --dma 6