diff --git a/full-tests/to-empty-main/src/main.rs b/full-tests/to-empty-main/src/main.rs
index 7f80c4e..2d13a58 100644
--- a/full-tests/to-empty-main/src/main.rs
+++ b/full-tests/to-empty-main/src/main.rs
@@ -9,4 +9,5 @@ fn user(mut map: HashMap<(), ()>) {
 fn main() {
     let map = HashMap::new();
     user(map);
+    "~REQUIRE-DELETED main-body";
 }
diff --git a/tests/full_tests.rs b/tests/full_tests.rs
index ed28255..b6e6025 100644
--- a/tests/full_tests.rs
+++ b/tests/full_tests.rs
@@ -16,6 +16,15 @@ use tempfile::TempDir;
 #[test]
 #[cfg_attr(not(unix), ignore = "FIXME: Make this not cursed.")]
 fn full_tests() -> Result<()> {
+    let exit = Command::new("cargo")
+        .arg("build")
+        .spawn()
+        .context("spawn: cargo build")?
+        .wait()
+        .context("wait: cargo build")?;
+
+    ensure!(exit.success(), "cargo build failed");
+
     let path = Path::new(file!())
         .canonicalize()?
         .parent()