diff --git a/tests/secp384r1-double/src/main.rs b/tests/secp384r1-double/src/main.rs
index a3b8a28ad3..b70b08773d 100644
--- a/tests/secp384r1-double/src/main.rs
+++ b/tests/secp384r1-double/src/main.rs
@@ -10,7 +10,7 @@ pub fn main() {
         // generator.
         // 26247035095799689268623156744566981891852923491109213387815615900925518854738050089022388053975719786650872476732087
         // 8325710961489029985546751289520108179287853048861315594709205902480503199884419224438643760392947333078086511627871
-        let a: [u8; 96] = [
+        let mut a: [u8; 96] = [
             183, 10, 118, 114, 56, 94, 84, 58, 108, 41, 85, 191, 93, 242, 2, 85, 56, 42, 84, 130,
             224, 65, 247, 89, 152, 155, 167, 139, 98, 59, 29, 110, 116, 173, 32, 243, 30, 199, 177,
             142, 55, 5, 139, 190, 34, 202, 135, 170, 95, 14, 234, 144, 124, 29, 67, 122, 157, 129,