diff --git a/Makefile b/Makefile
index e1164428..f9e62d7e 100644
--- a/Makefile
+++ b/Makefile
@@ -19,7 +19,7 @@ OBJ := $(SRC:.c=.o)
 
 # define default flags, and override to append mandatory flags
 ARFLAGS := rcs
-CFLAGS := -O3 -Wall -Wextra -Wshadow -pedantic
+CFLAGS ?= -O3 -Wall -Wextra -Wshadow -pedantic
 override CFLAGS += -std=c11 -fPIC -fvisibility=hidden
 override CFLAGS += -Ilib/src -Ilib/src/wasm -Ilib/include