diff --git a/fuzz/README.md b/fuzz/README.md
index f59418cfd..dfa90fc0f 100644
--- a/fuzz/README.md
+++ b/fuzz/README.md
@@ -80,6 +80,7 @@ mkdir -p ./test_cases/$TARGET
 echo $HEX | xxd -r -p > ./test_cases/$TARGET/any_filename_works
 
 export RUST_BACKTRACE=1
+export RUSTFLAGS="--cfg=fuzzing"
 cargo test
 ```