diff --git a/bootstrap.sh b/bootstrap.sh
index cf2cd9b..f154ad9 100755
--- a/bootstrap.sh
+++ b/bootstrap.sh
@@ -16,6 +16,7 @@
     dev)
         FLAGS="-Wformat -Werror=format-security"
         FLAGS="${FLAGS} -Werror=array-bounds"
+        FLAGS="${FLAGS} -Werror=implicit-function-declaration"
         FLAGS="${FLAGS} -fsanitize=address,leak,undefined"
         FLAGS="${FLAGS} -ggdb"
         ./configure \