diff --git a/board/bf527-ezkit/config.mk b/board/bf527-ezkit/config.mk
index 799a682..b3ed337 100644
--- a/board/bf527-ezkit/config.mk
+++ b/board/bf527-ezkit/config.mk
@@ -25,3 +25,4 @@
 
 CFLAGS_lib += -O2
 CFLAGS_lib/lzma += -O2
+CFLAGS_lib/zlib += -O2