diff --git a/hfuzz/test.sh b/hfuzz/test.sh
index eab042b..17fa42c 100755
--- a/hfuzz/test.sh
+++ b/hfuzz/test.sh
@@ -2,4 +2,8 @@
 
 export HFUZZ_RUN_ARGS="--max_file_size 2048"
 
+die() { echo "$*"; exit 1; }
+
+command -v wasm || die "spec interpreter 'wasm' is not on PATH";
+
 rustup run nightly cargo hfuzz run hfuzz